Enquiry (first published 1969)
Excellent - a real cracker of a story, fast-paced and extremely well written, about a jockey being 'warned off' for cheating at a race (I am not spoiling the story - this is all on page one!). He knows he didn't do it - and intends to find out who is behind the false accusations. Francis has you vehemently on the jockey's side, raging against the injustice, the being sneered at, the taunts. And somehow he gets you slowly falling in love, along with the jockey falling in love, as well.
The characters are well fleshed out, the dialogue is believable, the research is impeccable.
Dick Francis writes so well that there does not seem to be a superfluous word in the book. A taut story, crafted by a master, and another absolute smasher!