If you love books both fiction and non fiction and want to save a few dollars BMV Books on Bloor St. W. is great place to shop. A huge store with a good variety of publications on just about everything. Chances are you'll go in looking for something specific and come out with a whole bunch of books that were just too tempting to pass up.
For the most part they specialize in newer publications though from time to time you can find older out of print publications. The place lacks the charm of some smaller used book stores (with that old book smell), but what it lacks in charm it makes up for in sheer volume and affordable pricing.
In addition to books you can also find DVDs, music CDs and even video games. Though there are good deals to be had I suggest hitting the bank machine before entering the store as to not deny yourself the many books and such that will meet your fancy.