The suggestions so far are just value guides. Is this what you are looking for or do you want book suggestions for reading and learning about paper money? If so, then it would be helpful to know what area of paper money you want to concentrate on. like coins, paper money has alot of different ways to collect. Usually people start with the current small size notes. In small size you can collect by district, web notes, star notes, error notes, silver certificates, legal tender notes and many more ways. I personally collect obso;ete notes from the county I live in. They are interesting and historically significant. The is also colonial notes from the states, continental notes, national bank notes, miltary payment certificates (MPC) and large size notes. All of these are open for a collector to get into and each one has books devoted to it. I would suggest picking one area and buying a book about it to build your collection from that point. After saying all that, if you want an all round general book to help you pick a direction I would suggest U. S. Paper Money Guide and Handbook by Carlson R. Chambliss. This book has a chapter on each of the areas you can go into containing alot of great information.