What I never liked much in books that should provide knowledge.

[Harald]

What I like best are books that show every step of a calculation in a lot of detail, and then, when it gets complicated and you could really do with some help, they simply say "as can be easily seen...".
While most of the time it might be my fault not "simply seeing" something, I do believe there are occasion where the author didn't have a clue either how to get from one statement to the next and desperately needed to somehow fill the gap.

Cheers,
Harald