These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Either Victor Frankenstein is a tragic and naive scientist who - in his enthusiasm - bit more off than he could chew and paid a horrible price and suffered too much for it and has every right to be emo about it OR selfish asshole who tried to keep his PR clean by abandoning the monster and got what was coming to him and he's being whiny about it.
And the monster is either a far bigger woobie than Vic could ever hope to be, abandoned by the only person he could possibly consider a parent, or a wangsty monster with a Freudian Excuse who needs to take responsibility for his actions?
Ho Yay: Victor's describes Henry Clerval in a way someone would describe their love interest. Heck, his description of Henry is more thorough than those of his fiancée, Elizabeth. And he reacts to Henry's murder more strongly than Elizabeth's murder, too!
It Gets Better: The first few chapters detail the back story of the sea captain who met the titular Doctor on his expedition to find the North Pole. If you didn't know that the novel was a Story Within a Story (Within a Story) you would read the opening thinking "Get to the unholy abominations against nature, already!"
There's a long segment where the Monster watches a family for about a year - his yearning for a mate comes from the young man being betrothed to an older woman from some exotic place, as well as his identification with Adam's desire for a mate in Milton's Paradise Lost.
Too Dumb to Live: Vic runs away from his successful experiment in creating life because it's ugly. Then he destroys the Bride he was making for it, causing the Creature to go on a rampage. All the Creature wanted was some familial love, and then a female companion. C'mere, Vic... we need to slap some of the stupid out of you. In fairness, he destroyed the mate for fear that, unlike his first creation, it would be a monster in manner as well as looks.
He's also worried that the two creations together could breed and create a race of monsters. Um... brilliant biologist and anatomist hasn't heard of tying tubes?
Worse: The book makes it fairly clear it was made from dead body parts, though on a finer level than seen in the movies (manipulation of individual nerves, etc). And he wonders why it looks ugly?!
It's specifically stated he tried to make it beautiful and perfectly formed and no scars or stitches or anything of the sort are ever mentioned. I get the impression it looked somewhat appealing, or at least not that ugly, until it started moving (and opening its strange eyes) at which point Uncanny Valley kicked in hard.
Victor was so engrossed in his experiment that he physically viewed the creature simply as a "creation", not quite noticing its appearance as a human-like being.
When the monster told Victor that he "would be with you on your wedding night" he took that to mean that the monster planned to kill him then, even though its modus operandi up to that point had been to target his loved ones. He prepares to confront the monster alone while leaving his new wife undefended; the monster kills her instead.
I Am Not Shazam: The name of the hunchbacked assistant is not Igor. Ygor is an unrelated character from the third and fourth movies, who had a broken neck and didn't really assist the Doctor (he's the main antagonist in fact).