Network Warrior, Second Edition is an update of the original (2007). The first volume was well worth reading, and this updated version is definitely on the “must read” list for anyone working with Cisco gear. Be aware that the book is Cisco-specific with regard to commands and vocabulary.
In the introduction, the author indicates that this book should be valuable to anyone with an entry-level Cisco-based skills (CCNA or better), but in my opinion it could also be useful to IT personnel who interact with network gear and are willing to do some additional background reading. For example, the book’s lucid explanation of why autonegotiation causes problems could be of immense value to server team/sysadmin types (although obviously the router/switch config command listings are of less value to that audience).
One caveat to this book is that it should probably not be read by those attempting the CCNA or CCENT until *after* successfully taking the exams, unless you are certain you can sort out the Cisco “textbook” material from the “real world” discussions in Network Warrior.
Overall, this is a great book, well written, clearly illustrated and with examples that are hauntingly familiar to anyone who has supported Cisco networks of significant size.