Whether your into anime or manga, read this book. If you are into manga it will tell you everything you ever wanted to know about the history and progression of the medium from it's earliest roots in ancient Japan and how American comics were a major influence (you heard right, and it's all come full circle). Sure it's a little dated (he doesn't think manga will ever become popular in the US -- never imagining that American readers would be more than happy to conform to the right-to-left reading style), but most of the info in there is as relevant today as it ever was because it's historical fact.
If you are an anime fan read it because manga is where anime got its start. So if you are reading the history of manga, you really are reading the history of anime too.
Just read it. Trust me. '^_^