Some of these giveaways are a bit out of date, but many of the books are still available for download. Many (not all) of the downloads require that you allow the author to contact you afterwards (you’re joining the author’s mailing list); for the others, joining the mailing list is optional. You can always unsubscribe later if you choose.
Click the images to go to the landing page for each giveaway.
And finally this promo includes both free and paid books: