I have a book by a Norwegian cook named Andreas Viestad. It's called "How to boil water" and I think its brilliant. In the book he spends most of the time discussing why and how certain techniques work etc. He also covers trvial stuff like prep work that some of us home cooks are never properly tough (first time I saw an artichoke I had no idea where to start). There are a few recipes as well but its also a book you can read from cover to cover.
Heston Blumenthal occasionally also takes the time to explain why things are done in a particular way and there are other authors as well. Any books you would like to recommend? Preferably with as much theory as possible!