This Indigo location is one of my favourites. They have the best selection of business books. Their hold/special services department is very helpful too.
This store does get quite busy, so if you are looking for a quiet corner to read in, go to indep book store Nicholas Hoare (http://www.yelp.ca/biz/nicholas-hoare-toronto) or off the main drag awesome coffee spot Merchants of Green Coffee (http://www.yelp.ca/biz/merchants-of-green-coffee-toronto).
This Indigo seems to be the flagship shop. If a celeb is going to be in town and sign their books - this is the spot. Strange they choose here actually as the lay out is quite tight and not much extra space is available.