Chris,
This bag comfortably houses the Alienware 17 R4 with room for a sizable amount of ancillary gear. I would say you could easily haul 4-5 books along with the laptop. Keep in mind though that you will be approaching a pretty heavy weight with such a loadout. Coming from someone who carried a lot of weight in college on a daily basis, her back would not thank her after 4 years of such treatment. As long as the secondary bag contents aren't crazy heavy, you certainly have the volume to fit them in this bag along with the laptop gear. I use the bag exclusively for hauling my laptop, mouse, and gaming headset and find it quite pleasant. With that loadout, it's a black hole of empty space waiting to be filled!