If you're tight on money, many good books can be had used. I recently got a copy of Tanenbaum's Distributed Systems book for a third of the cover price.
I forgot to mention that most of the books I bought are used. They are a lot cheaper sometimes and are in perfect conditions. The last one I've bought, "It's Not How Good You Are, It's How Good You Want to Be" by Paul Arden cost me only 0.01 pounds(without shipping). It is used but like new. Awesome purchase