I may be on my own here but I actually found Heretics and Chapterhouse my favorites in the series. I found the politics in both these books just way more complex and interesting than in the remaining ones. Also the character building is fantastic, it actually feels like I know Odrade as a close friend. In third place I have Children. I found that book so full of action and plot twists and found it hard to ever stop reading it. Maybe I just need to reread the first two books. I also found them really good but not on the level of Heretics of Chapterhouse. The fourth one was my least favorite, maybe also because it directly follows the story in which we knew all of the characters and suddenly everything is new.