For Kicks (1965) by Dick Francis
"The English Earl of October tries to hire Australian horse breeder Daniel Roke to find out how someone is giving race horses a drug to win races that does not show up in drug scans. Although he initially resists, he agrees and goes undercover as a stable boy. In this guise, he is able to see and hear all that happens as he goes from stable to stable. In the process he gets to know Elinor, the Earl of October's younger daughter, and they become friends and perhaps a bit more. When he does finally figure out what is going on, not only is he in danger from the people behind it, but Elinor is as well. When he is forced to deal with them, he ends up in jail and only the Earl of October can get him out because it is his older daughter who has accused him. Unfortunately, the Earl is away at the moment. Can Daniel get out of jail? Can he prove who is behind the horse drugging scandal? Will he and Elinor get out of this alive? Read For Kicks to find out! "
I'm turning off the comments for this post because my other DF review gets like 20 Chinese spam posts a month!
This really is one of the better of Francis' books. The author was big on class and gets caught up in exposing class injustice at times. The story though ratchets up the tension throughout and makes this one a crackerjack book.