Audio Mashup Construction Kit: ExtremeTech This book is really for mashup production, but has techinques that are very useful for remixing and gives a good music theory introduction.
The ones on mixing and mastering are especially useful, for example how to properly set up the studio to avoid hot spots and how to construct some cheap sound absorption/traps.
The advantage of the DVD is actually seeing how to put this stuff together.
I also like Microsound by Curtis Roads. It's not the easiest read, but it's been a book that I've gotten several useful techniques from that I otherwise wouldn't have thought about.