I just have to say....I hate the Unofficial Guide. I love the work Len Testa did on queuing theory, the rest of the book I despise. Bought it to get the queuing theory stuff, and because so many people here love that book. I think its overly negative. Its poorly designed and badly organized for my needs. In places its just plain wrong - and those errors seem more frequent than the other major books. He presents opinion as fact. The book is too long, and most of it has been written by people sending in comments!
So, before you invest in any book, check them out at the library, or plan to spend an hour in a chair at Barnes and Noble browsing them. Just because someone else loves (or hates) a book doesn't mean it will be the book for you.