It says:

Hundreds of free books by some of the greatest Catholic authors ever delivered to your email weekly ~ 100% FREE with no obligation.

I'm thinking about joining. Does anyone here belong?

https://ucatholic.leadpages.co/catholic-book-club-ty/

I've found these sorts of things to be:

"We find old, royalty free books that you could get for free on Amazon or Project Gutenberg and harvest your email information in exchange for them..."

But if you don't know about those books in the first place, you aren't going to be able to find them. And by the way, there is no such thing as 'free' on Amazon, not permanently so. There is a requirement that there be a price of at least $0.99 even for works in the public domain. The owner is allowed to offer the books free for a limited time as a promotion, but not permanently. And most of the $0.99 books are poorly formatted crap that are virtually impossible to actually read.

My Kindle has more "free" public domain books from Amazon than I will ever be able to read.

Go to Amazon>Kindle ebooks> type "Catholic" in the search window the sort the results by price low to high.

I just scrolled through 14 pages of free Kindle books and I'd not yet hit a book that cost more than 0.00

Temporarily free