I like reading anything remotely about horse racing. Of my books listed on Goodreads (basically every non-fiction book I've read the last six years), 60 of 98 concern the sport of kings. I'm not really into fiction or mystery but I do enjoy Dick Francis. I just finished Blood Sport, the 21st Dick Francis book I've read since starting with Odds Against six years ago. His books are short, relatively simple, and his heroes are easy to identify with. Francis wrote a book a year between 1962 and 2000, took a few years off after the death of his wife and has been back to a book a year since 2006. Here is a website whose author provides summaries of and rates each mystery. I use it as my checklist so I've read all of the high rated books. My favorites are For Kicks, Banker, and Bonecrack.

The only other horse racing mystery write I am aware of is William Murray. I enjoyed Tip on a Dead Crab and have bought but have yet to read any of his other mysteries.