GetBackers館　〜　GetBackersグッズエクスプレス　〜

This book is quite fun to read, but not flawless, as the story goes to a new section, it's normal that the introduction parts are a bit boring.
One negative point is that, under a quite exaggerating background, the story/abilities/breasts are sometimes even more exaggerating, making the story a bit childish.
But still worth a read.