In the topsy-turvy world of publishing, books remain a fundamental source of information for developers at Dr. Dobbs journal.
I have found that I really need the physical book to effectively absorb certain kinds of information, and learning computer languages is definitely one of those. I bought the Agile Web Programming with Rails book as a PDF (twice), the pickaxe Ruby book, Rails Recipes and a bunch others. I learned lots from them, and used them as a daily reference for over a year.
Then, I finally broke down and got the books, and I'm amazed at how much more I get out of the paper book. I think one of the big things is that I can chill out on the couch and just slowly peruse it, without all the energy and distractions of the computer. But in any case, I just love paper books, and I would like you to try out that experiment as well, try absorbing a book as a PDF, and then get the paper version.
If you buy your books at Pragmatic Programmers, they give you a great deal on a PDF/Book combo and they're really nice people too.