I’ve wasted a lot of money on lousy programming books over the years, but I’ve also found a few jewels that stand out. This is a short list of books I have found to be extremely helpful in Drupal development.
#1. Pro Drupal Development by John VanDyk: I think it is fair to say that this is the undisputed bible of Drupal. In the forward written by Dries Buytaert (the programmer who invented Drupal), Dries states that he doesn’t know of one single Drupal developer who doesn’t own this book. I myself have to agree. Anyone serious about Drupal owns this book. John did an amazing job covering the workings of the Drupal Api. The examples in the book are practical and well written, the writing style is clear and to the point and all the information is well categorized and easy to find. I can’t say enough good things about it. One thing you should realize however is that the author approaches the subject with the assumption that you already understand PHP, CSS and programming in general.
#2. PHP 5 Recipes a problem solution approach by Lee Babin: Before I found this book I had bought several other books that aimed to teach you PHP. I was surprised to find however that I learned more from this book (which really doesn’t make the claim of teaching you PHP) than I did with all of the others combined. I found that the way PHP 5 recipes focuses in on specific problems with small code snippets is much easier to digest and more practical in the short term and the long term. I found that the majority of books that try to teach you PHP as a whole waste a lot of time using code examples that are completely inapplicable to the Drupal content management system. PHP 5 recipes keeps it simple and rather than having you put together whole PHP systems which handle database server authorization on each page or other absurdities, it sticks to helping you solve real world problems that arise in programming. Classified by subject matter it is easy to find solutions to problems you will inevitably encounter while writing modules. I recommend this book to any level of programmer from novice to professional.
#3. JQuery in Action by Bear Bibeault and Yehuda Katz: This book is I think the best book that I have found for really getting a handle on what JQuery is and how to use it correctly and effectively. They start off by building the theoretical foundations piece by piece and make the JQuery library make sense. Its writing is impeccably well structured and organized and by the time I was done reading it I felt confident jumping into writing JQuery (I wrote the Jquery menu module shortly after reading this book).
#4. Learning JQuery: While JQuery in action really does a good job at dealing with the theory of JQuery, Learning JQuery spends much more time dedicated to practical examples. I see this book as a good companion book to JQuery in Action because it gives a wider spectrum of code to analyze and make use of. I don’t recommend buying without JQuery in Action though since it is very weak on the explanation element which JQuery in Action Excels in.