This is undoubtedly the best available introduction to Western art. Although designed primarily for the college textbook market, where it is the leading one-semester text, it should also appeal to the lay reader. The hardback edition is beautifully produced and should find a place on many coffee tables. The illustrations are generally of a very high quality (most of them are in color).
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College Art History
This book has wonderful pictures and gives an excellent overview from ancient to post modernism art. The descriptions are pretty brief though, and do not go into great detail on any particular artist. However, it's an excellent book to get a general idea of the evolution of western art. The book covers significant art movements, and some minor ones as well.