I agree with Joe K.'s review; this book does a good job of building on the foundation established by the BulletJournal.com site and extending it for us in RPGs.
I've been bullet journaling for the last two years or so for my work and home life. Extending it to RPGs is something I experimented with, but didn't get very far. Taking a step back and reading "Bullet Journaling for Gamemasters" helped me gather and organize my own thoughts on how to apply the bullet journals to my campaigns.
The addition of photos to the book helped me visualize what the author was shooting for. While the the concepts themselves are easy to grasp, it's always nice to see how folks implemented them.
The spreads themselves are straightforward and hew closely to bullet journaling at its more Spartan end, so don't expect wild and crazy designs for habit trackers or funky-looking logs. That's not a criticism; it's a design choice that I appreciate.
I can see this book evolving over time to incorporate different kinds of collections, spreads, and logs, but its definitely a solid introduction for using bullet journals for your game.