This is a good book. However It is written in a bit of a disjointed fashion, bouncing around from 2001 to 1950 to 1989 etc. I had a bit of trouble putting it all together because of this distracting presentation. But I also read it in bits and snitches and it may be that it is partially my fault that I didn't pull it all together. Probably a 4.0, but my rating is 3.6. I should probably re-read it, but I have to move on to other things.