Well I can't say I disliked any of the Discworld novels, every single is brilliant (we are talking about Terry Pratchett

).
I think that Pratchett writes for everybody. Some of his works I find SUPERB - the Witches, Tiffany, Death... I couldn't believe anyone could write such a marvelous book as Maskerade, this is my all-time favourite book.
I read Guards! Guards!, and it was nice, but I didn't get the WOW feeling I got when reading about the witches... I don't know, I guess I never really liked Carrot, Vimes and Nobby... But Lady Sybil was great...
So, I must say, Guards! Guards! wasn't as good as other Discworld books. But I'm sure there are people who just love it.