If you can only purchase one book to prepare for your coding interview, without a doubt, the absolute best use of your money would be to purchase “Cracking the Coding Interview” by Gayle Laakmann McDowell. The problems and questions outlined in the book are extremely representative of what most big technology companies are using these days. In fact, many people have reported to receiving questions directly from the book itself. Do yourself a favor and pick up a copy today!
Another invaluable resource for all those attempting to get a job building software or studying computer science is “The Algorithm Design Manual” by Steven S Skiena. It is actually one of the books specifically recommended by Google for all individuals interviewing with them. It provides an easy to understand approach and discussion on many of the various algorithms encountered in the realm of software engineering and computer science.