I recently moved to Canada & have managed to accumulate so many books. I mostly get my books from book outlet. I shared my first experience with them here. I also try to buy from independent bookstores with my favorite being BMV Books. If you live in Nigeria, you can get your books from Bookpeddler, Serenebox, BookMarketng, & pagebookstore. Check them out. I’m sure they’ll have the books you’re looking to buy.