Jack Reacher stays the course as Lee Child hands author’s reins to his brother Andrew Grant

The author of the immensely popular series says his days as a novelist are over. He’s still listed as co-author of ‘The Sentinel,’ a thriller largely written by his novelist brother.

The longtime author of the immensely popular series says his days as a novelist are over, even though he’s still listed as co-author of ‘The Sentinel,’ a thriller largely written by his novelist brother, who has assumed responsibility for continuing the popular franchise.

The cover of “The Sentinel” (Delacorte Press, $28.99), the 25th thriller in the wildly popular Jack Reacher series, says it was written by Lee Child and Andrew Child, though no one by either name actually wrote the book.

Reacher’s creator Lee Child, whose real name is Lee Grant, has said his days as a novelist are over. Lately, he’s been working with Amazon to develop a Jack Reacher TV show starring Alan Ritchson, an actor as enormous and menacing as the character in the books — and a welcome change from the height-challenged Tom Cruise, who played the role in two Hollywood movies.

But Reacher, the mythic avenger who wanders the back roads of America like a modern-day Lone Ranger, is too popular with readers to just fade away. So Grant (aka Child), has turned the series over to his younger brother Andrew Grant, the author of nine thrillers published under his real name.

It’s Andrew who wrote most of “The Sentinel.” But, because the names “Child” and Reacher” are forever bound together, he adopted the pen name Andrew Child to carry the series into the future.

The change in authors is subtle but detectable. For one thing, the technologically averse Reacher has now acquired a cell phone. For another, the hero has become a bit chatty, talking more with other characters and telling readers more about his thinking — including how he maps out in advance the hand-to-hand he’ll engage in with thugs who outnumber him.

The story begins when Reacher wanders into the little town of Pleasantville, Tennessee, where Rusty Rutherford, a nerdy IT manager, is being blamed for a cyber-attack that wiped out the town’s computer data.

After rescuing Rutherford from a kidnaping attempt, Reacher gradually discovers that the seemingly isolated attack is part of a conspiracy to undermine the coming national election.

As always in the series, the bad guys — Russian spies and American-Nazi thugs this time — discover too late that they are no match for Reacher.

Despite the change in authors, the writing remains tight, and the non-stop action is as propulsive as ever.