"a nice overview"
I enjoyed this book and felt the earlier reviews were unfair. If you expect to learn everything there is to know about music history in 10 hours, then your expectations are too high. This is a good starting point if you don't know much about classical music, or it can be a refresher if you are like me and have studied the subject in the past.
The book gives you the framework and the music recommendations to expand your knowledge. To learn more, you'll want to spend time exploring the music that is referenced.