Some of the books also ventured pretty close to darkness, Night Watch had humorist tracesd, but mostly it was a timejump back into a bleak, darker past.
I agree. Night Watch made me laugh, and angry and scared at the same time. All wrapped up in superb writing. After reading the book (a few times) I decided Sir Pterry had reached the top of his game.
... And then I read Thud. And then Snuff. Stunning books, that really made me think about some of the terrible issues we're still trying to deal with in our own Roundworld!