I picked this book up on my honeymoon in Japan in 2014, so it’s weirdly special in that sense. The book was originally released in 2013, and covers every game in the series, with a focus on the (then recent) PSO 2.
There is art and information about each pre-PSO 2 game. A few interviews are included as well (in Japanese, of course).
The bulk of the book is focused on Phantasy Star Online 2. It’s really interesting to look at now, as I’m actually familiar with the game’s early NPCs. If you’re currently playing PSO 2, you’ll definitely recognize some of these faces!
The book closes with A TON of PSO 2 concept art, something I always find fascinating.