We have The Sibley Guide to Birds. It's put out by the National Audubon Society. This book has a wide variety of birds found throughout the U.S.
If you get a chance you might consider attending a local Audubon Society meeting if there's one in your area. If you decide to join the dues are really inexpensive. Our dues are $20/year. They have monthly meetings with a variety of speakers. Some local Audubon groups have a number of field trips throughout the year where you can do some bird watching with some knowledgeable folks.
Good luck with your birding. We enjoy the birds and have a handful of feeders in our yard.