While other commenters are correct that manual QA is a mindset, there are readings that can help develop that mindset.

I have new QA engineers read the first five or six chapters of "Testing Computer Software":

http://www.amazon.com/Testing-Computer-Software-2nd-Edition/...

to get a feel for the mindset and methodologies and to help them understand what testing can and can't accomplish.

"Lessons Learned in Software Testing", mentioned by another commenter, is another good resource. Lots of good anecdotes:

http://www.amazon.com/Lessons-Learned-Software-Testing-Conte...

Both are a bit dated in some ways ("Testing" has a section on filing paper bug reports), but the lessons and thinking are still highly relevant.