I'd suggest you to read 'The Art of Unit Testing', by Roy Osherove. I strongly recommend you to read Parts 1 and 4.
Although focused on Unit Testing (duh) there are some well-explained concepts that really helped me to understand better the world of testing. It's not a complicated / boring book, I enjoyed reading it even without any previous testing knowledge. Hope you enjoy it too.
About unit testing here is very good book: http://www.amazon.com/Art-Unit-Testing-Examples-Net/dp/1933988274
The Astels book is a solid introduction, Beck's book is good on the underlying concepts, Lasse Koskela has a newish one (Test Driven: TDD and Acceptance TDD for Java Developers). Osherove's book, as he says, is about Unit Testing, rather than TDD. I'm not sure that the Pragmatics' TDD book has aged as well as their original book.
Most everything is Java or C#, but you should be able to figure it out yourself.