Horror isn't usually my thing, and if the Fantasy Bingo didn't require me to find at least one for the Horror field, I wouldn't have picked up The Library at Mount Char. Fortunately for me, I can't say that I found Mount Char particularly close to horror (still gonna count it for the bingo though). Rather, it felt like a darkly humorous Hitchhiker's Guide with more plot coherence.
For the first three quarters, the book is a fast-paced dark magic adventure as the protagonist is killed, framed for murder, busted out of prison and kidnapped in that order by the deuteragonist. Oddly though, the climax then happens at said 75% of the story, which then flounders for the last quarter of the book as Hawkins struggles to neatly wrap up the conclusion.
Still, the first three quarters are excellent, and the remaining quarter is still competently written, so a solid 4/5 from me.