I would suggest visiting one of the Salvation Army thrift stores in Hamilton... they usually have a large book section that has cheap paperback novels and such.
And then I'd also just suggest you try the library located in the core of downtown hamilton, lots of good reads, updated often (usually 1-2 copies of new books), you can even then browse online in the catelogue and put books on hold so they'll go and pick them out for you and have them bundled and waiting for you when you get there! And its free! can't beat that lol.
But if you're wanting to buy books and have them forever.. here's some stores
The Westdale Bookworm (905) 523-4345 852 King Street West, Hamilton
It's an interesting store... lots of hard to find books, fiction, etc.
Hours: Mon - Fri: 10am to 6pm, Sat: 10am to 5pm. Closed Sun
Sells: used books, rare, out of print, science fiction, paperbacks
Allan Petteplace Bookseller (905) 521-5535 23 King William Hamilton ON
Barely Bent Used Books (905) 628-7862 46 KingE Dundas ON
Barone's Books (905) 544-4240 1925 King E Hamilton ON
Bill's Used Books & Records (905) 741-0938 250 King W Hamilton ON
Book Gallery-John Stirling (905) 627-5008 212 Hatt Dundas ON
Chapman Books (905) 627-5007 11 Cross Dundas ON
Hamilton Book Company (905) 521-6444 Hamilton ON
J & F Hobbies (905) 528-5236 413 Whitney Ave Hamilton ON
Mountain Bookstore (905) 385-6082 560 Concession Hamilton ON
Tucker Plus (905) 522-9251 159 John S Hamilton ON
World Of Books (905) 523-5107 150 James St S Hamilton ON