Crusher, a "gritty" London-set thriller about a 17-year-old school dropout who finds his stepfather murdered and becomes prime suspect for the crime, will be published by the Doubleday young adult imprint in September.
Leonard is a TV screenwriter with credits including "Hornblower", "Wire in the Blood" and "Monarch of the Glen". Crusher is his first novel and he originally intended to self-publish it after writing it during National Novel Writing Month last November.
RHCP fiction publisher Annie Eaton bought world rights in Crusher and two other books through a deal with Valerie Hoskins of Valerie Hoskins Associates. She called Crusher an "electrifying story" and Leonard "a fantastic new voice for teenagers".
Leonard said: "Crusher is a story I have wanted to write for years and it finally all came together last November when my wife encouraged me to take part in the Nanowrimo novel-writing event. I am thrilled and delighted that RHCP have picked up Crusher for publication, and it's a fantastic honour to join the distinguished names on their writers' list."
The novel is thought to have adult crossover potential, with writer Simon Kernick calling it "a fast-paced thriller with real heart".