Some of the books I have include:

Title Author ISBN Comments
Dorling Kindersley Handbooks: Birds of Canada Fred J. Alsop III 1-55363-011-4 My newest and soon to be favorite combined with the Sibley Guide.  Highly recommend this.
National Audubon Society: The Sibley Guide to Birds David Allen Sibley 0-679-45122-6 Wow.  That was my first impression.  A very good book.
Stokes Field Guide to Birds, Eastern Region Donald and Lillian Stokes 0-316-81809-7 My first field guide.  Photo based rather than drawings (ie Sibley).
Birds at your Feeder, A Guide to Feeding Habits, Behavior, Distribution and Abundance Erica H. Dunn & Diane L. Tessaglia-Hymes 0-393-32231-9 A interesting collection of information from Project Feeder Watch.   More information on this project is available at Cornell Laboratory of Orthinology or Bird Studies Canada
National Audubon Society: The Sibley Guide to Bird Life and Behavior Sibley, Elphick & Dunning 0-679-45123-4 The perfect complement to the Sibley Guide above.  More information than most of us amateurs want to know, but a good starting point to expand your knowledge base
The Peterson Field Guide Series: Feeder Birds, Eastern North America Roger Tory Peterson 0-618-05944-X A great book for the house, and kid/senior friendly too.  Large pictures and fonts