Willow Books is an unassuming kind of place you frequently walk by (it's right beside the Bata Shoe Museum), assuming it's not worth looking into. That would be a terrible assumption to make, as this bookstore is like a miniature, messier version of NYC's The Strand or Portland's Powell's . With new, used and rare books at extremely reasonable prices, it turns out this is a book browser's paradise.
The original location used to be on Bathurst, but it moved to Bloor a few years ago. This space is a labyrinth of half-levels, with a huge selection of poetry and plays and a great little children's nook as well. The store buys and sells used U of T textbooks and also has a textbook rental program.
There is also an ongoing "buy one book, get the second at half price" deal that started off as temporary but seems to be sticking...