Horowitz is the latest contemporary novelist to be officially commissioned by the Fleming estate to write a continuation novel. He said he intended to "go back to the true Bond" with his own creation, after being given access to original material from Fleming's own notepad.
Publishers said: "Fleming's text sees Bond in the high-octane world of motor racing and it is his never-used plot that kicks off the action of Trigger Mortis."
The author, who has also written a Sherlock Holmes continuation novel, was given permission to study a script for Murder on Wheels, an episode of a television series that was never made. In the plot, James Bond is called into M's office for a mission to make sure that a Russian plot to sabotage Sir Stirling Moss is intercepted.
Horowitz, writer of the bestselling Alex Rider series, Midsomer Murders and Foyle's War, said: "It was always my intention to go back to the true Bond, which is to say, the Bond that Fleming created and it was a fantastic bonus having some original, unseen material from the master to launch my story.
Trigger Mortis will be released on September 8, which would have been Fleming's 107th birthday.
Lucy Fleming, his niece, said: "What a brilliant birthday present for Ian - Anthony has written a James Bond book with a nail-biting adventure that could have come from Ian's own typewriter."