A novel about Colorado and a large book in every sense of the word, Centennial is one of Michener's most successful outings. It boasts the humongous timeline we've come to expect from him, but the fiction itself rests on a solid foundation of fascinating historical facts. Exposition abounds, of course, but in this case it's well balanced against the human stories.
Michener starts with a somewhat didactic geology lesson and gamely presents us with the personal trials and tribulations of dinosaurs and early mammals, followed by.. um, beavers? Well, beavers can have rich and emotional inner lives, too. Heck, you can tell the man even did massive research into beavers. This is a very dedicated writer, folks.
Anyway, the human part of the book starts with the first inhabitants of the area, the Arapaho, and their initial encounter with whites. This portion has some of the most interesting characters, the Arapaho chief Lame Beaver and the intrepid French trader Pasqinel. These people are so colorful they must surely be based on real historical figures.
There's a particularly disturbing massacre about a third of the way through the novel (basically the Sand Creek Massacre). Sad that so little of the horrific details of this event had to be made up by the author. (Truth is often worse than any nightmare one can dream up.)
An impressive pageant of characters wander in and out the pages of this book; it'd be a slog to go through them all. You have your usual black hats and white hats, a generous amount of gray characters, and a generous sprinkling of under-developed walk on parts. It's an engrossing and informative read, not high literature, but by Michener standards pretty good.