I own one of these shotguns. The layout and operating controls are indeed similar to the AR-15, with the exception of a bolt mounted operating handle on the right side, but the internal mechanics and operating system are more akin to to a Remington 1100 semi auto shotgun than an AR-15. I have two 10 round mags and two 5 round mags and the thing is as smooth as butter and really puts pellets down range FAST!!
I recently picked a VEPR 12, right before the magazine ban in Colorado went into effect. No shotgun magazine of more than 8 rounds can now be (legally) sold or transferred in Colorado, so I made sure to picked up some 12 round magazines before the law kicked in.