Diane Duane is an American fantasy and science-fiction author now living in Ireland. She was born in 1952, was first published in 1979, and has been writing sci-fi and speculative fiction almost continuously ever since. She has written in a lot of different universes. Here we go:
The Young Wizards multiverse. This seems like it would fit in the "young adult" genre when you first pick it up; that facade is the book preparing to grab you by the heart and squeeze. The series details the adventures of Nita Callahan and Kit Rodigruez, who are chosen by the Powers That Be to become wizards and to help fight the Lone Power, creator of entropy, death, and most of the evil in the multiverse. Toward that end, they begin to learn the Speech, which is essentially the language in which the multiverse is "programmed". The Speech is used, among other things, for the creation and execution of spells, but calling it "magic" isn't quite right—all spells have to obey various scientific principles, most notably the laws of thermodynamics. Due to its multi-universal nature, the Young Wizards 'verse has connections to many of Duane's other works.
The Book of Night with Moon (or Feline Wizards) Same 'verse, different protagonists. Centers around a team of cats who maintain the worldgates (wizardly mass transit system).
Stealing the Elf-King's Roses: Primarily set in two alternate universes which are part of the same "sheaf" of universes as ours. This sheaf of universes has developed worldgates which allow for routine interdimensional transportation and communications. Interuniversal relations are generally peaceful, but when a new one is discovered, things start to get messy. The book focuses on Lee Enfield, a detective who serves the deific manifestation of justice.
Omnitopia Dawn: First in a projected series, this book describes a financial and electronic war against the perfect MMORPG.
The Tale of the Five: Duane's first series, still unfinished. A fantasy series with unconventional ideas about human relationships and sexuality.
Star Trek: In addition to writing several comics and part of a TNG episode, Duane has written a number of Star Trek novels; these are generally regarded as among the best of the best by fans, although they occasionally contradict canon established in later books and films.
The Wounded Sky, an exploration of what happens when time no longer exists and a hole is ripped in the fabric of the universe. So, pretty much business as usual. What really put it on the map is that it also explores the true essence of the Enterprise crew.
Spock's World, about the history of Vulcan and its possible secession from the Federation. Also, McCoy giving the entire Vulcan race a verbal spanking.
Doctor's Orders: what happens when McCoy is left in command of the Enterprise. (Answer: hilarity. And a little bit of heartwarming.)
The Rihannsu series, which delves even more in-depth into Romulan and Vulcan culture, and is generally the foundation for fanon concerning said species.
Dark Mirror, in which the Enterprise-D is abducted by the Mirror Universe. Later contradicted by Deep Space Nine which established that the Terran Empire had fallen after Mirror-Spock tried to reform it.
Intellivore, regarding a mobile soul-eating planet which is even more terrifying than it sounds.
The Harbinger trilogy, for the Star*Drive RPG 'verse.
McCoy to the Klingon commander Kaiev in ''Doctor's Orders":
McCoy: If you use that tone with me again, my boy, I'll open your ship up like a sardine tin, and later on I'll fish your corpse out of space and thaw it out and stitch it back together the old-fashioned way, with a needle and thread, and then I'll use your guts for garters.
And of course, he was bluffing. He'd never do anything like that!
At another point in the same book:
Think again, Commander. This is Enterprise. She is more than one man, though that one man may have made her famous — or among you, infamous. She is four hundred thirty-eight people — to whom you're an interesting enough problem, but one that we're long used to solving.
McCoy all but turns these into a language of their own in this book, as he never speaks to a Klingon in anything but one the whole time he is in command.
In The Wounded Sky, "a bawdy ballad about the (improbable) offspring of the marriage between an Altasa and a Vulcan" is mentioned. It's a Shout-Out and Stealth Pun at once— the original song is an Irish folk song about a Catholic and Protestant couple's child.
Oh I was the strangest kiddie that you ever have seen My mother, she was orange and my father, he was green...
In that same book, we learn that "the filthiest spacers' song" that Captain Kirk knows is called "The Weird-Looking Thing With All The Eyes And The Asteroid-Miner's Daughter".
In Honor Blade a Rihannsu song called "The High Queen's Bastard Daughter" is mentioned twice, but no lyrics are given.
Bridge Bunnies: Strongly subverted, especially with Uhura. One example in Spock's World is when Kirk casually asks her about how one of her dissertations is shaping up, and she launches into a head-spinningly complex discussion of alien syntaxes, translation algorithms, and xenolinguistics that leaves Kirk utterly in the dust, privately ashamed for ever thinking that Uhura's job was some kind of glorified switchboard operator.
The USS Inaieu is a gigantic version of the Enterprise, with four warp engines.
The Bloodwing in the Rihannsu series. How cool? Well, it regularly defeats ships that are bigger and more powerful, including the Enterprise (to be fair, the Enterprise was the one ship that had defeated Bloodwing, and they were about the same number of victories). Also, Romulan ships tend to have cool names or be named after cool people, things or legends, like the Rhea's Helm (see Jackass Genie entry for what it was named after).
Exact Words: In My Enemy, My Ally, Kirk asks Ael for whom the Rihannsu ship Rea's Helm was named:
Ael:You would have liked him, Captain. He was a magician whose enemies captured him and forced him to use his arts for them. They told him they wanted him to make a helmet that would make the person who wore it proof against wounds. So he did - and when one of those who captured him tried it on, the demon Rea had bound inside the helmet bit the man's head off. A corpse will not care how you wound it...
Note that Rihannsu is a Retcon name for Romulans (here said to be just a human code name for them, explaining its source in Earth mythology), later adopted by other Star Trek authors - for example in Diane Carey's Final Frontier, a Rihannsu first hears the word 'Romulan' and considers it to be rather vulgar-sounding.
McCoy's epic filibuster in the Romulan Senate, to delay his execution until rescue can arrive.
McCoy does it again in Spock's World, giving a speech denouncing the calls for Vulcan secession. His speech is met with a standing ovation.
Hot Scientist: Duane deliberately played with this in the back-cover blurb for The Wounded Sky, describing K't'lk as "a pretty alien scientist" while distinctly failing to mention that she is also a giant glass spider.
In My Language That Sounds Like: In My Enemy, My Ally, "Jim" means something hilarious in Romulan, but we never find out whatnote It simply sounds really, really like a very rude word in Rihannsu: hence Ael's reaction on hearing it first. (Cf. the reaction of some immigrants from Germany whose names produce problems on being translated into English: "Oh good, my name has only one obscenity in it.") —DD
Jossed: As published novels, Duane's books are considered "soft canon", but elements of them have been discredited by later onscreen revelations. Notably, her deep and nuanced portrayal of the Romulans was very popular among readers, but was disliked by Gene Roddenberry, who felt she had strayed too far from his original vision.
Language Equals Thought: It's mentioned that the Orion Pirates' word for "stealing" translates into English as "getting paid".
Little Green Men: Parodied in Spock's World when Amanda's response to a reporter's question is "There's nothing little about my husband."
Used by Picard to hide things from Mirror Troi in Dark Mirror
Also used twice over in Intellivore, by Picard and another captain on their quest to destroy the Intellivore. One involves the conventional kind of static, while the other involves hooking Data up to the Enterprise computer and putting everyone else on the ship to sleep.
Residual Self Image: In The Wounded Sky every time the Enterprise uses the experimental drive, the crew members experience a reality based on how they perceive themselves. While Kirk's self-perception is never actually described, McCoy provides a solid clue when he asks "Is that armor getting heavy, Jim?"
Also, The War mentioned in The Romulan Way. The aliens kidnapped the Vulcan ambassadors and tried to hold them for ransom. The Vulcans developed advanced sublight drives from the remains of the ships formerly of the pirates.
Sapient Cetaceans: : Dark Mirror involves an alien race that's essentially dolphins IN SPACE! (They're not related to the whales IN SPACE from Star Trek IV.) Young Wizards also features Cetacean wizards (the Trek novel contains a Shout-Out to them). Of course, pretty much everyone and everything with more brains than a sponge has Wizarding potential in this setting.
Shown Their Work: It's truly surprising how much a reader can learn about astronomy from her books, not to mention various fictional treatises on the histories of Vulcan, the Romulan Star Empire, and the Alpha Quadrant, just to name a few.
A young (pre-Surak) Vulcan couple in Spock's World
As well as young Sarek and Amanda. The trope is usually phrased something like: "They then realized that they would have to get married in order to have the time to argue properly."
Starfish Aliens: A number of examples, most of whom are in the Enterprise crew. And the Denebian starship Inaeiu, which is a supersized Constitution-class ship with four warp engines crewed entirely by Starfish Aliens.
Scotty and K't'lk in The Wounded Sky. They quite literally can't, what with her being a giant spider, but they really, really want to. To the point where she adds an 's' to her name after her death in honor of him.
Kick the Dog: Near the beginning of Omnitopia Dawn, we are introduced to Delia Harrington, an investigative reporter. She's just been assigned to do a story on Dev Logan, another of the book's main characters, and she's certain that the incredibly positive reputation he and his company have acquired must be a sham. Okay, we think, she's a reporter: ferreting out the darker parts of human nature and bringing them to light is part of her job. It's not until she rolls down her window and yells "Idiot!" at someone in traffic that we realize that this is not intended to be a sympathetic character.
Meaningful Name: Dev Logan (from Omnitopia Dawn). "Dev" in an MMO context usually stands for "Developer".
Sliding Scale of Idealism Versus Cynicism: Invoked in Stealing the Elf-King's Roses, which was written right after 9/11. A major plot point is that a group of parallel universes discovers our universe, and we're much further down the scale than they are. This is incredibly disturbing from their point of view.