Robin Hobb's Farseer trilogy were the first books that I really hated.
I must have been about fourteen or fifteen when I first read them. Up until that point, my reading had pretty much solely consisted of either crime novels (Arthur Conan Doyle, Agatha Christie), or anything written by Bernard Cornwell. They were the sort of books where the hero always unequivocally triumphed. I thus wasn't quite prepared for a series of novels where the likeable protagonist had to deal with the unfair fallout from his decisions, where bad things happened for no good reading, and where the story ended in a bittersweet and untriumphant place.
But although I hated them, I found them compelling and readable, and a year later I decided to try them again (I re-read everything in those days). By that point I'd gained a bit more emotionally maturity, and suddenly the complexities that I'd previously found unsatisfying felt fascinating and right. For a long while, the Farseer trilogy were probably my favourite novels.
The story is narrated by Fitz, a royal bastard, as he struggles to navigate the fantasy medieval court of Buckkeep. An overarching plot-line about a conflict with the Red Ship Raiders, and Fitz's links to a boyish prophet known as the Fool slowly emerges - but really, much of the interest in the series comes from the interactions between the subtly drawn characters that Fitz encounters at Court.
However, the thing that most influenced my development as a writer were the climaxes that Robin Hobb wrote for the first two books.
I think of them as Don Giovanni climaxes.
Essentially, at the end of Don Giovanni, the Don sits down to dinner whilst his manservant, Leporello, attends him. The music starts off fairly jovially, with snatches of music from other popular operas woven in - until Dona Elvira comes racing into the room. From this point onward, a succession of escalating crises is reflected in the noticeable gear-changes that the music undergoes. The score gets tenser and tenser, until with the violins going haywire, the chorus howling, and the core singers pretty much spitting at each other, the Don is dragged down to hell by a crowd of demons (they didn't do things by half at the end of the eighteenth century).
Robin Hobb's novels Assassin's Apprentice and Royal Assassin follow a similar formula. The characters face a problem that has been mounting over the course of the novel, and so they finally decide to do something about it. When they put their plan into action, however, little things start to go wrong. But that's not a problem - because they can correct the original plan to suit their new circumstances. However, in making their course corrects, other, slightly more serious things start to derail. As this process is repeated, the plot rapidly snowballs, until the characters are having to make devastating decisions simply to survive the chaos that they have unleashed.
It's a type of climax that I've always loved (although Hobb herself seems to favour more subtle endings these days). So it's hardly surprising that, when I came to write The Not So Fairy Tale Princess, this was the formula for the ending that I chose to follow.
By the way - if you have never read the Farseer trilogy, I recommend that you go and pick it up now.