One of the absolute best introductions to art is not a book but rather a documentary series called Simon Schama's The Power of Art. The show goes above and beyond a simple linear historical narrative. It was produced by the BBC and deconstructs eight works of art and their accompanying historical context. There is an accompanying book of the same name that I haven't read, but I have heard is a useful addition.

The Power of Art is NOT a generalist introduction to the subject, but one that is selective in its focus to argue for the importance of art through history.

When I took a lot of art history in college (6 or 7 classes that covered 5,000 years of the stuff, with my favorite covering 18th and 19th century American Art ) the classes that were most successful were ones that sought to describe why art was meaningful, why it could be seen as a reflection of the culture of its creation. Part of this was driven by my desire as an artist to figure out why art mattered. This meant fewer facts, and a greater appreciation for historical and cultural context.

Janson's History of Art has long been the standard issue Art History 101 textbook, with good reason; it's thorough, accessible and nicely, voluminously illustrated.