Not all that much, unfortunately. There is just the general synopsis of the setting and some mentions here and there (like, there is a Ma. K movie supposedly in the works?!). Most of it focuses on the models themselves, although every model has some descriptive lore text regarding its background.
Having bought the digital version, I think it's a bit unfairly priced considering the content. It would be a much more agreeable proposition at 15$ or something like that, but yeh. The models themselves are to die for as usual tho!