I've not read Dick Francis before, and probably wouldn't have except for J S Borthwick having one of her characters, Aunt Julia, read and like his books. That small positive inclusion by a cosy mystery writer I like has added an author to my list.
Comeback was an interesting mystery, the world of horse obviously strong and the characters clear. The tension was sufficient to keep me reading. I'll read more of Dick Francis's books, but not because they're must-reads. More because they fill time pleasantly. Still, that's more than you can say of many books. Another plus is that the books are readily available in libraries and cheaply in secondhand stores.