Tyndale Rewards is a program that gives you the opportunity to earn free books when you take surveys, review products, refer friends, share links on social media, and more.
It looks like you could fairly easily earn 1-3 books per month by investing a little bit of time a few times each month toward the earning opportunities.
Get 25 free points when you sign up here.
(Note: The link in this post is my referral link. Read my disclosure policy here.)