Northern & Central Midwest
Although not a new book, Second Nature: A Gardener's Education, by Michael Pollan (Dell Publishing, 1991; $14), is still one I periodically pull out to read because it's such a delight. Pollan is a wonderful observer of the idiosyncracies and delights of the garden, and he also makes many observations about gardeners and the rest of the world. All in all, this book is a delightful read, especially in the hammock on a warm summer day.
U.S. National Arboretum
To be on the cutting edge of new trees and shrubs, visit the National Arboretum Web page. It has plenty of information about gardening, plant introductions, ongoing research, and events at the arboretum. If you're planning to be in Washington, D.C., this summer, this is a source for checking out events before you go.