I feel I must have written about this before but it appears not.
I like French folds, they add gravitas and style to what would otherwise be an ordinary paperback. A French fold is a continuation of the book cover that folds inwards and thus can be used as a bookmark. It also allows artwork on the cover to flow onto the fold. Some sources suggest that publishers choose carefully which books will have this treatment and it does indeed make it special in a very satisfying way. I don’t seek out books with French folds but it is a treat when I come across one.