Christianbook is a great resource to buy Christian books, Bibles, recources, and various other things at great prices.
This site is a great place for discounted Bibles, study resources, gifts, homeschool resources, christian books and so much more. Check it out to build up your library. There are hundreds of books on various topics and tracts for evaneglism.
On top of the discounted prices, often times there is free shipping applied at checkout.