For me it was a trip down memory lane. The book includes interviews with the founders of Usenet and with the pioneers who contributed to its character and growth. The authors make good use of an archive of the first few years of Usenet postings. Those of us who were there remember much, but the archive is like putting history on videotape.
Several chapters tell the history of many of the building blocks of the Internet.
Netizens also tells the story of the UNIX operating system, how it came about, the key contributors, even how the grep command got its name. Photos from the 1950s showing computer center machine rooms with IBM 704 components taking up the entire room, key researchers at places like MIT, computer chess tournaments, and the founders of Usenet add to the sense of history. This is an excellent book. The academic style means you'll have to think to read it. This book is a vital element in any Internet historian's library.