Up until a few years ago, reprint rights were the big dog on the block. Your publisher would acquire the rights to your book and produce it in hard cover. That was the way things were done for the most part. Any other form of the book was something they could license, so they could license paperback rights or mass-market rights (mass-market paperbacks are the ones that fit on the racks you see in the supermarket). That arrangement still exists, but publishing companies have acquired other publishing companies and become conglomerates, so they often have the ability to do paperbacks within their own organizations. As a result, the author will rarely see more money from reprint rights. The book stays within the Random House empire or the Penguin empire or whatever through all its incarnations.
In the old days, rights directors paid their mortgages by having auctions for books. Two or three companies would compete for the rights to a book, and they would end up paying six or even seven figures. That has changed, but you can still make money from reprint rights. I work with a self-published author who has made a deal for the mass-market addition of his westerns, which sell for about $7.99, but keeps selling self-published hard cover copies for $25.00. The two don’t really compete, because they appeal to different audiences, so nobody minds this arrangement. He’s still selling his hard covers, and I’ve licensed the mass-market paperback. I’ve also licensed a large-print edition for the same author. Westerns are popular with an older demographic, so they’re good candidates for large-print editions. There are two companies that specialize in this area, Thorndike and Center Point, and you try to make a deal with one of them. It’s not necessarily money you can fly to Paris with, but it means another source of regular checks for the author, and it also means the book is reaching a different audience than it otherwise might. The days of big auctions and multimillion dollar bids are gone, but reprint rights are still an important area to explore.