I'm a well read grad student who's bluntly honest about all things, although I try to be most honest about myself.
The illustrations are nice, but there aren't enough that aren't covers, or things that I've seen, to make this worth buying. I'm glad I got it from the library, in fact!
Also, I had zero interest in the illustrations from the game. The explanations of how she did some things, or what the covers were supposed to mean, were neat, but again, not worth the price of this book. There was nothing that felt special or like a revelation.
I'd suggest just reading the manga.