In A Brother's Price, Odelia sees Jerin's face for some seconds when (after she was unconscious for a time) she opens her eyes, and he murmurs something comforting. That's enough to make her decide that she must, if not more, at least get a kiss from him. Justified by the lack of men, and Jerin is rather handsome. It's left unclear how strong her feelings are, exactly (not that she'd be able to judge it, she can't have much experience with love), but she's willing to pretend unconsciousness, which must be quite boring, in the hopes that he will spend more time with her.
Happens to Kim Ward and Jelka Tolonen in David Wingrove's Chung Kuo series.
The two protagonists of Anthem, Equality and Liberty, fall in love the second they meet.
In Five Hundred Years After, Aliera and Mario fall in love almost immediately, despite him being an assassin fleeing after attempting to kill the Emperor. However, this may be Paarfi's embellishment.
In Dragon Bones, there's a rather realistic example with Ward, who, when he first meets Tisala, can't keep his eyes off her, even though he remarks that there are many other beautiful women at the table, and she isn't even conventionally beautiful at all. It is obvious to the reader that he's smitten with her, as she gets a very detailed description, and he notices that he's fascinated. Later on, when he rejects another woman, she suspects that he'd prefer Tisala. He doesn't call it love in his inner monologue, but as they do end up together eventually, and he immediately remembers her fondly when he sees her again, and admits that he compared all other women to her it is pretty obviously this trope.
Also counts as Love at First Note; Amberley was posing as a (very talented) cabaret singer at the time.
A humorous version in the latest book of the Wheel of Time, in which Berelain (The Vamp, who seduces people for political advantage) and Galad (an exaggeration of the Knight in Shining Armor) both fall head-over-heels on their first meeting. This leads to many entertaining scenes, especially as both of them are presented earlier as cool-headed and in control.
Played for laughs in Which Witch? where Belladonna falls in love with Arriman after witnessing a rather short speech by him. She's very impressed by the antlers he attached to his head, and his dark and evil appearance. (He's a dark wizard, and endeavours to look the part). He later falls in love with her in an equally silly manner, and gets on everyone's nerves by insisting that they have to marry now.
Harry Potter crushes on Cho the instant he sees her during a Quiddich match in his third year. It doesn't last...
GinnyWeasley's reaction to Harry from the moment she meets him. That one sticks.
Nine-year-old Severus Snape seems completely entranced by little Lily Evans from the moment he lays eyes on her.
In Dan Abnett's Gaunt's Ghosts novel The Guns of Tanith, Milo, reflecting on his not present love, considers Caffran and Cridd and their sweet romance, even though neither of them would describe it as love as first sight. (From their actual meetings in Necropolis, they might be wrong not to do so.)
In G. K. Chesterton's Tales of the Long Bow, Owen Hood habitually fishes a certain location in hopes of meeting again a woman he had met only once:
Years before, when he was a very young man, he had sat fishing on that island one evening as the twilight bands turned to dark, and two or three broad bands of silver were all that was left of the sunset behind the darkening trees. The birds were dropping out of the sky and there was no noise except the soft noises of the river. Suddenly, and without a sound, as comes a veritable vision, a girl had come out of the woods opposite. She spoke to him across the stream, asking him he hardly knew what, which he answered he hardly knew how. She was dressed in white and carried a bunch of bluebells loose in her hand; her hair in a straight fringe of gold was low on her forehead; she was pale like ivory, and her pale eyelids had a sort of flutter as of nervous emotion.
Parodied in the Discworld novel Sourcery, where Nijel and Conina first meet: "The world had suddenly separated into two parts — the bit which contained Nijel and Conina, and the bit which contained everything else. The air between them crackled. Probably, in their half, a distant orchestra was playing, bluebirds were tweeting, little pink clouds were barrelling through the sky, and all the other things that happen at times like this."
I loved Dejah Thoris. The touch of my arm upon her naked shoulder had spoken to me in words I would not mistake, and I knew that I had loved her since the first moment that my eyes had met hers that first time in the plaza of the dead city of Korad.
From Skulduggery Pleasant, China Sorrows has the ability to make everyone she meets fall in love with her. Skulduggery says that the effects lessen over time but will never go away completely.
Hell's Gate by David Weber features one group of people with a variety of psychic talents. Voices are the most common power, and are telepathic. Recognition between telepaths is very rare, but happens enough that it is the standard for most great works of Romance and tragety in the world. Two persons who've never met lock eyes and just suddendly are in love. But they don't know each other, and may already be married to other people.
The werewolves in the Twilight series undergoes a process called imprinting, which alludes to animals' instinctive and overpowering attachment to their young. However the effect is complicated by the fact that the werewolf can imprint on any human (in one case, a baby), and it can also happen when he or she is already in love with someone else.
"Baby" being minutes after she's born.
Implied that it had already happened before she was born and that that was the reason he stayed for the entire pregnancy, and that he just mistook it for his feelings for Bella. Which is even squickier.
"Hey, Nessie, remember when I was trying to bang your mom?"
Twilight in general takes this to...rather extreme measures at times. There's a trend in predestination amongst the couples. An example of this would be Alice, who fell in love with Jasper before first sight (she foresaw meeting him and thus went to where they'd meet).
Another variant: Edward falls in Love At First Smell with Bella.
In Mirror Dance, mother and son discuss father and mother's meeting:
"He thought it was love at first sight. I've never bothered explaining to him that it was his compulsions leaping up." "Why not? Or were your compulsions leaping up too?" "No, it took me, oh, four or five more days to come completely unglued. Well, three days, anyway."
Averted in the Darkest Powers series by Chloe and Derek that it's worth mentioning. First of all, they meet in a group home for "troubled" kids, which is a code word for "mentally disturbed" (which is a code word for "has superpowers"). Derek assumes that Chloe is a flightyblondeditz whose only point of interest is the fact that she's a necromancer, and only because he can use her to manipulate his brother, Simon, into finally escaping to safety. As for physical attraction, he doesn't even notice her looks (although she is legitimately cute). On Chloe's end of things, Derek is initially withdrawn, ominous, intimidating, and a Jerk Ass. He has also been viciously mauled by (werewolf) puberty, so his face looks like a "before" picture for acne cream, his hair is constantly greasy, lank, and dull, and the deodorant does nothing — even though he showers twice a day. The first time they're alone together, the interaction goes downhill, until Derek ends up throwing her across the room. It's an accident — actually an accident, not "Why'd you make me hit you, baby?" — but Chloe doesn't know that until a few chapters laternote When she does find out how he could manage to throw her across the room without putting deliberate effort into it, she accepts the explanation. It helps that she weighs maybe a 100 pounds and is only five feet tall, and he's over 220 pounds of pure muscle and roughly six-three or so.. At the end of the trilogy, they end up together after their relationships develops in a completely believable manner, turning out to be the complete opposite of Strangled by the Red String.
As a matter of fact, Talia and Dirk did this too. Dirk was the first Herald that Talia saw!
In The Tale of Genji a man doesn't have to see the girl to fall in love - fortunately as women normally hide behind curtains and screens. Just a glimpse of her perfect calligraphy will do the job nicely. If he does manage to get a peek at her the results will be instantly devastating and probably lead to all kinds of complications.
Later on in Conan's life, in "The Hour of the Dragon", Conan has already become a King but is defeated in battle, dethroned and held captive in a dungeon at hostile Nemedia. When suddenly the slave girl Zenobia appears at the door of Conan's cell and offers to free him, he is initially suspicious of her motives. She explains: "I have loved you, King Conan, ever since I saw you riding at the head of your knights when you visited King Nimed years ago. My heart tugged at its strings to leap from my bosom and fall in the dust of the street under your horse's hooves". She is the first of the very many women Conan had known who makes him think seriously of marriage.
J. R. R. Tolkien liked this one, both Beren and Aragorn were devastated by their first look at Lúthien and Arwen on The Silmarillion and Lord of the Rings, respectively. Tolkien himself fell for his wife Edith when he was only sixteen, proposing marriage and being accepted the day after he turned twenty one.
Agatha Christie also favored this trope. Many of her short stories involve young couples deciding to marry hours and several adventures after their first meeting. Sometimes justified in-universe, inasmuch as the circumstances of the adventures have shown each half of these partnerships exactly what the other half is made of, and by taking place in a culture noted for relatively brief courtships.
S.L. Viehl likes to play with this trope in various ways.
In The Picture of Dorian Gray, by Oscar Wilde, Basil Hallward falls for Dorian when he sees him at a party, leading him to paint the titular portrait. Then Harry Wotton gets in the way and things go... poorly.
Miguel de Unamuno's novella Mist (original title: Niebla) has the main character, Augusto, fall in love with Eugenia as they pass by each other on the street. Everybody supports their relationship except for Eugenia, who is in a relationship with somebody else.
In The Sword and the Circle, Rosemary Sutcliff's retelling of the first part of the Arthurian legend, eighteen-year-old Arthur falls in love with Guinevere at first sight, though he doesn't realise it initially. Then Lancelot and Guinevere fall in love with each other the moment they accidentally touch hands and look up into each other's eyes.
Stu Redman and Frannie Goldsmith in Stephen King's The Stand...Stu told Frannie it took about three hours, but the text of the scene where they meet indicates it may have been even a bit faster.
In Edgar Rice Burroughs's The Monster Men, Number 13 falls in love with Virginia at once, though he does not fathom it. When he recovers from amnesia, he explains that he had fallen in love at a train station and chased after her across the world.
In Gene Stratton-Porter's The Song of the Cardinal, the cardinal had actually met the she-cardinal before, and kissed her, but the circumstances meant he had not noticed her much. But when she flies to his tree, he is struck down, his usual Pride humbled, and he sets out to woo her.
instantly this shy little creature, slipping along near earth, taking a surreptitious peep at him, made him feel a very small bird, and he certainly never before had felt small.
My natural sensibility had already been greatly affected by the sufferings of the unfortunate stranger and no sooner did I first behold him, than I felt that on him the happiness or Misery of my future Life must depend.
Discussed in Golden, a retelling of "Rapunzel": Rue is skeptical that the prince could truly love her right after seeing her for the first time, especially since he had been talking before to the real Rapunzel (who kept out of his sight because of her baldness), but Rapunzel tells her that while true love does take time to develop, there's always that one moment when the seed for it is planted, whether it's a glimpse of a beautiful woman in a tower or a prince ready to sweep you off your feet, and sometimes you just have to take a leap of faith to let it grow and blossom.
Played painfully straight in Zel, another retelling of Rapunzel, however: Prince Konrad's five-minute encounter with Zel apparently had such a powerful impact on him that he turns down multiple arranged marriages and goes on a two-year quest to find this peasant girl he once gave a goose egg to.
In Patricia A. McKillip's "The Kelpie", Ned is embarrassed to do it, but admits to Emma at their first meeting that he's never felt about anyone as about her, and she admits the same. They discuss getting to know each other better.
In the Chivalric RomanceSir Degrevant, while Degrevant is fighting an neighboring lord, he catches a glimpse of his daughter Melidor, and falls instantly in love.
The Grass Is Singing by Doris Lessing has an example that is such a heavy deconstruction it might not even count as that any more so much as someone just being Wrong Genre Savvy. Dick Turner sees a glimpse of a beautiful woman in a movie theatre. Though he's introduced to some rather unremarkable woman whom he gives a lift home from the theatre, all he can think about is this one he saw. Later, he returns to the town and asks to be introduced to her. It turns out it's the same woman he took home, Mary, who just doesn't look at all as interesting unless seen in and from just that light and angle. They marry soon anyway because both just feel they need to find someone. It doesn't work out well, not even before the part where one of them winds up dead and the other insane.
In John C. Wright's The Hermetic Millenia, the Nymphs are capable of inducing this biochemically. Oenoe had agreed to it, to transfer her hopeless love, and accidentally transfered it to one knight guarding the Tombs.
In Just One Day by Gayle Forman, Allyson falls in love with Willem, a Dutch boy she meets while taking a tour of Europe. She runs off with him to Paris and loses her virginity to him, and wakes up the next day with him gone. The rest of the book is about her journey to find him again.
Anna and Vronsky in Anna Karenina are a deconstruction of the trope. It's Love at First Sight, and Anna gives up her entire life just to be with him — but then they have to deal with what happens when that initual fascination isn't enough to sustain a relationship.
In Andre Norton's Ice Crown, downplayed. Roane merely finds the first look at Nelis Imfray rather interesting, though he's not so good looking as her cousin.
The Apprentice Rogue: This is what Artamos feels when he sees Leona. She admits to the same at the end, just before they have sex.
In Victoria Forester's The Girl Who Could Fly, Boris falls in love with Lily on arrival. Fortunately, this gives him a motivation to help all those strange kids with their dangerous plan on his first day at the school.
In Stephanie Burgis's A Most Improper Magick, Elissa is much taken with Mr. Collingwood at their first meeting, but, as she explains to Kat, he's Unable to Support a Wife, let alone provide the money her family needs, so she must not even consider him.
The Hunger Games: Peeta's been in love with Katniss since he was five. His father was similarly in love with Katniss's mother, who chose a miner instead, because when he'd sing, the birds would listen. When Katniss sang in front of their entire class on the first day of school, the birds stopped to listen — and at that moment, Peeta was a goner. There wasn't going to be anyone else for him after that. And it sticks. The last chapter and the epilogue of Mockingjay reveal that the two have fallen in love, married, and had children together.
Hunger Games is an interesting example because in the third book Peeta actually falls out of love with Katniss after being subjected to brainwashing designed to make him fear and hate her. He eventually falls back in love with her but this time he's acknowledged her bad qualities and genuinely grows to love her for who she is rather than love the idealized version of her like he did before.
August sees a picture of a woman in a locket that he finds and suddenly falls in love with her, and then consequently berates himself for losing his mind.
Aiden and Lilac fall mutually in love within moments of meeting each other but both have rather strong emotional baggage with regards to relationships and the two are overwhelmed by how their emotions escalated so quickly for one another, and can't bring themselves to fully acknowledge their feelings.
In the Honor Harrington short story "Beauty and the Beast", Honor's parents, Alfred and Allison, had a mutual case of this, helped in part by Alfred's low-level telepathy, causing the two to form a Treecat-like bond. Given that this is the Honorverse, however, they spend quite a bit of time avoiding each other and lambasting themselves for thinking that it could actually be real until Allison gets kidnapped.
In Katherine Paterson's Of Nightingales Who Weep, Takiko falls in love with Hideo when she first meets him at the temple, even though she realizes that he is an enemy spy; she struggles to do her duty when it endangers him. It ends in Old Flame Fizzle.
In Eric Flint's 1632 series, Mike Stearns falls for Rebecca Abrabanel in the space of about two seconds, and Jeff Higgins falls for Gretchen Richter even faster. Both of those marriages stick.
A racial trait of the elves in The Riftwar Cycle is the Recognition: most elves have an instinctive recognition of who their mate will be.
Son has Andras fall in love with Claire as soon as he sees her and is lovesick over her until her pregnancy is revealed.
Romans seem oddly prone to this. One might expect the somewhat ditzy Pompey to fall for the woman promised to him as his wife practically as soon as he lays eyes on her but it comes as a surprise when the level headed, indeed cold blooded, Octavian falls instantly in love with Livia.
This happens to Geryon and Herakles in Autobiography of Red. Geryon sees Herakles getting off a bus, and
. . . there it was one of those moments that is the opposite of blindness. The world poured back and forth between their eyes once or twice.
The Witcher Saga plays with this. Geralt and Yennefer seemingly fall for one another within their first meeting in "The Last Wish." However, they have a very dysfunctional relationship where they often fight, cheat on one another, break up, and make up numerous times over the years. It's not until Ciri enters the picture where they finally reach some form of stability in taking her in as their adopted daughter.
In This Immortal, Conrad and Cassandra fell in love on their first chance meeting shortly before the beginning of the book. Apparently, it took them only two months to get married.
In the comic fantasy novel The Dragon Hoard, people fall in love this way more often than not. In particular, it happens to the protagonist, Prince Jasleth, when he meets Princess Jadelli (and vice versa), which causes a certain amount of subsequent awkwardness because they're both aware that if he succeeds at his quest the results may be bad for her people.
The Mary Russell novels have a one-sided example, where her eventual husband fell in love with her at first sight — or at least, that's what he claims when she eventually realizes that she loves him. She reminds him that when he first saw her he mistook her for a boy, and he replies, "Yes, and don't think that wasn't disconcerting."
In the Elemental Masters series, Elemental masters and mages, thanks to their magic, are often able to recognize their True Love on sight, usually resulting in a Fourth Date Marriage. (Sometimes not even that, since one character notes that he's heard of mages/masters meeting for the first time and then are eloping the next week in Gretna Green, not having the patience to get a marriage license and post banns.)
The Stormlight Archive: Shallan falls head over heels in love with Adolin pretty much as soon as she lays eyes on him, which he reciprocates. In fact, they first meet when he sees her through a crowd of people and runs over to her—though in fairness, he did recognize her as the girl he was supposed to marry.
In Warrior Cats, Storm and Clear Sky can't help but stare at each other throughout their first meeting, and they become mates shortly afterward.
In David Weber's Safehold series, King Cayleb of Charis proposes marriage, sight unseen, to Queen Sharleyan of Chisholm in a cold-blooded political move to unite their kingdoms and hopefully survive the oncoming war against their planet's corrupt church. The first time they lay eyes on each other, to their own initial dismay they turn into giddy, lovestruck teenagers, and they go on to have one of the most roaringly successful Perfectly Arranged Marriages in all of literature. Oh yeah, and they win the war, too.
In the novella A Taste of Honey, the story is kicked off by Lucrio calling out from a doorway to a passing Aqib about how beautiful the latter is. They both know it's love after exchanging a few words. The end reveals that Lucrio was counting on falling in love at first sight, and let it happen, because the Sybil had told him he'd find his love in Olorum.
In The Sorcerer of the Wildeeps, Demane remembers meeting Isa in a market square in Philipiya and immediately offering him to come sleep at his place in the amir's palace instead of the travelers' barracks. When Isa just as immediately tells him his full name and takes his hand, they both know it's true love, and Demane gives up his post at the amir's court to become a mercenary at Isa's side.