Gampuku is Akira Hiramoto's art book filled in with his godtier lewd ecchi drawings: lots of focus on boobs and ass based on the cast of his previous manga Prison School. Akira has a new publishing manga called 'RaW Hero', which also contains really lewd scenes.
Besides the very lewd drawings, Akira can also draw very realistic drawings whom are also really great. But this is obviously not the selling point of this artbook..
A must buy artbook if you love extremely lewd artwork, because this one of the few ones you can buy.