In Child's books, Reacher is described as 6ft 5in tall with hands the size of dinner plates. Cruise is 5ft 7in.
"Cruise, for all his talent, didn't have that physicality," Child told BBC Radio Manchester's Mike Sweeney.
The author said a deal was signed last week to make a new streaming show.
Readers had complained about Cruise's suitability to play the imposing former major in the US military police since his casting was announced in 2011.
"I really enjoyed working with Cruise. He's a really, really nice guy. We had a lot of fun," Child told the station.