It goes against all the tastes you'd expect from me - but Good Omens. Lovely concept, lovely characters, but I can't stand 200-page tangents and 50 perspectives with introductions to every scene from their POV. It's like Prachett and Gaiman had a great soup but decided a gallon of water was just the thing to finish it.
It's odd too, I read Witches Abroad before this and it's also full of tangent, but I think it hits less because you're always following the witches or the events in the city. Good Omens shifts perspective SO. MANY. TIMES. And they're just there for jokes instead of progressing anything, sometimes up until the end of that perspective part. I stopped around the part Anathema and the witch-finder guy started putting things together because I legitimately didn't remember what was happening with half the cast anymore, yet I was reading it almost daily.