As a huge fan of Klingons, I really enjoyed this sourcebook. It's set in the pre-alternate timeline universe, which I prefer. Even though I really like Discovery, their Klingons haven't grown on me yet.
Included in this book are rules for creating, arming and playing a Klingon as well as an introductory adventure and several ideas on other adventure and campaign possibilities. Also included are stats for many of the Klingons introduced in the various Star Trek TV shows and movies, again only pre-alternate timeline. I do wish that listed with these NPCs were the episodes or movies they appeared in for easy reference, especially for those readers less familiar with the shows.
My favorite part of this rulebook were the descriptions of the other races and political bodies from the Klingon perspective. Anyone who wants to play a Klingon should definitely read through these to get into the Klingon mindset and I certainly consider it mandatory reading for any GM who is going to use a Klingon NPC.
Overall, this is a great book when it comes to capturing the feel and character of the Klingon people.
[5 of 5 Stars!]