'1491: New Revelations of the Americas Before Columbus' by Charles Mann
Most of what you find written about pre-conquest "Indians" is broken apart along modern political boundaries. For example, it's hard to get a sense of a culture when part of the culture is written about only in books about Colorado and part of it only in books about Mexico. A great achievement of this book is the ignoring of modern political boundaries and looking at the great sweep of cultures that were here pre-Columbus, pre-smallpox.
This book is important because it talks about something most modern white Americans would rather not talk or think or even know about: Before our European ancestors arrived, the continent was full of people. People of many languages and cultures, as distinctive, complex, and advanced as any in the "old world." Cultures that are now utterly lost.
I still find books about "the Indians" that describe their idyllic, simple life, plucking the fruits of an Eden that only exists in European fantasies. The way our great-great-great grandparents imagined it, and we don't want to hear a different message. In correcting that view, "1491" may be a path back to sanity.
But the book is NOT one of those downer everything-is-doomed Sierra Club magazine books. It's not a bone dry academic book either. It is a fine, journalistic overview of an enormous topic, lively and fascinating reading. It's a big thick book, but I flew right through those pages.
Charles Mann is a journalist covering technology, commerce, and science. His website is at www.charlesmann.org.