I get daily emails with lots of free book downloads from:
www.pixelofink.com and also
www.inspiredreads.com.
www.diningdownloads has recipes and cookbooks. The books that aren't free are usually $2.99 or less. You have to "buy" the books, even if there is no charge for it. I'm not sure how many books a Kindle will hold, but I'm up to about 875 now.