As the title suggests, this book is about BGP4, period. Don't expect a big discussion about anything else. There is an obligatory intro to internet routing and TCP/IP, but that's not the focus of the book. What it is is a great first book on BGP for anyone looking to use multiple ISPs for corporate internet access, or looking to implement BGP4 on larger corporate intranets.
The description of the BGP4 routing protocol is extremely detailed and would probably serve as an excellent reference guide. There are enough examples to give you a pretty good idea of how BGP is used, but if you're looking to create your own autonomous system(s), you'll need more information. Check out Bassam Halabi's book - Internet Routing Architectures and talk to your ISPs routing experts. btw: Halabi's book focuses on Cisco's implementation of BGP4 and includes lots of example configs, but that's fine since the internet is dominated by Cisco anyway.
I found this book to be excellent and recommend it to anyone who is interested in implementing BGP4 in their network, or to anyone who just wants to expand their knowledge base. The book is short but that's a positive attribute in this case. Kudos to Mr. Stewart.