Online books were covered briefly in a node above, but that is where it is at! I really like the online versions of O'Reilly Books
. Much easier to search for reference points, as well as bookmark. I find my traditional "dead tree" books start to look like ugly bushes with all the post-it notes sprouting from them.
Try the online books, the advantage is having things written with teaching/learning as a more focal point rather than documetation which has a different approach. They are both useful, and while good documentation is golden, a well written book is priceless, regardless of how it is displayed."Nothing is sure but death and taxes" I say combine the two and its death to all taxes!