If you do a fair bit of work with Shimano components, then... the Shimano tech data sheets are pretty darned useful. Along with the instructions that come with various components you might use.

Barnett's is great if you want to understand why things are done. Big Blue is a good reference, but just seems to lack enough detail for my liking. Brandt's wheel book is over-indulgent for the here and now, but is a useful reference. Zinn is OK, although I only ever looked at one of his earlier publications and wasn't overly thrilled about it.

The swipe at people using books not being good mechanics just doesn't make sense. Everyone has to update their knowledge irrespective of their field of expertise, and in cycling particularly with the changes that are occurring with things like headsets and BBs. I would prefer being serviced by a mechanic who reads and keeps up with what those developments are... if I was going to use a shop mechanic, that is.