CCNA is one of the fastest growing certifications in the computer industry and there are so many books on the subject that it's hard to make a choice sometimes. If there was a book that would give you what you need and make it easy to understand you would buy it, right?
Maybe you check out CCNA Certification by Prentice Hall. Starting with the OSI model then moving to Hardware devices, followed up with TCP/IP, you have a great starting point. Also there is great overview of other CISCO switches and routers and for the test this is very handy.
There is one of the best breakdowns of TCP/IP addressing and subnetting I have ever read. The author simplifies static and dynamic routing, IPX/SPX, access lists and managing the router. There is also a chapter on router commands and extra features, another useful tool in passing the exam.
Appendix A is the answers to the practice questions, Appendix B is practice exercises and C is command structure and a cd with helpful utilities is also included. The only drawback to the whole book is there is no page numbers making it difficult to find things. Overall this book will give you everything you need to pass and for the money a good purchase.