I think I read 'em all! When he comes out with a new one, I get it on the spot. The latest that I read was Second Wind, a nifty little story about a sports reporter who ends up fighting for his life in a hurricane.
I first heard of Dick Francis when one of his stories was featured in the USAn Public Television program "Mystery." I don't know which of his stories it was, but since then I've been hooked.
This is one caveat to people who've met up with Francis's stories first on the small screen: the stories can be quite freely adapted. The latest one that I saw, based on Odds Against, was such a horrible adaptation that it was practically unrecognizable. In that case, at least, the book was really much better.
Learn more about Dick Francis here.