I like the "In a Nutshell" books by O'Rielly for learning stuff quickly. I may even have "Java in a Nutshell" at home. I don't think I have it as an e-book, but I'll check later.
I find Interactive CD-Roms the fastest way to learn a new programming language, but I'm a visual/practical learner so it may not work for you. I learnt the basics of Javascript in one weekend - 15hr course.