If you want friends to actually read a book you recommend, have them buy it themselves. Then refund them after they finish. People follow through on things they paid for, even if you cover the cost later.
You ever read a book and it's like, oh, it's so good, and you want your friends to read it? This is how I actually get my friends to read the books I want them to read. So I tell them, buy it with your own money and then read it, and then once you've read it, I'll refund you the money. That makes sure that they actually check it out because nobody respects free, let's just be honest. Also works for courses. Try it out, let me know.
