No single source will both cover the exam AND teach you all the theory and background.
Ideally, I recommend having both exam study guides and building a personal technical library with books such as from ARRL, college texts, The Art of Electronics, and older texts and courses available online.
I use a mix of techniques, but in the end use the exam book as 'study guide'.
-Read the questions, cover the answers. If I get the answer wrong, then refer to other books for more knowledge until I understand the material. I highlight the answers, mark up the questions and answers with notes, make a master list of formulas, and make flash cards as I work along. http://www.tubebooks.org/technical_books_online.htm
Many excellent technical books and electronics courses.