Your school will make recommendations as far as books and required supplies. Some programs want specific nursing drug books and nursing diagnosis handbooks. Other schools just say get a drug handbook and nursing diagnosis book. While the extra information is helpful, it may be an added expense if you purchase the wrong version/publisher. If you haven't completed pre-req courses yet, you can try some of the supplemental books such as Anatomy Coloring Book, Physiology Coloring Book, Microbiology Demystified or Microbiology made easy.
You can check your program requirements, some schools provide a list of supplies other schools require students to purchase a kit of specific supplies (stethoscope, blood pressure kit, clamps, scissors, watch, clip board, penlight, etc.) We were given a list of supplies to purchase such as BP cuff, scope, scissors, penlight, etc. Our book list was made available approximately 3-4 months in advance including recommended and required titles complete with ISBN numbers so that we could shop around for the best deal. Do you know your course outline yet? (Such as first semester is fundamentals of nursing...)
You can also purchase an NCLEX prep book as that will likely be helpful throughout your program. Some people like the Demystified and Made Incredibly Easy, and Exam Cram books as they break down the concepts rather well. You can find the books in major book retailers as well as online.