There are a bunch of "as by someone". See https://embden11.home.xs4all.nl/Engels7/demille.htm

TitleYearUS 1stUS 1st SgndOther
The Sniper (Also published in 1989 as by Jack Cannon)1974
The Hammer of God (Also published in 1989 as by Jack Cannon)1974
The Terrorists (written by Leonard Levinson)1974
The Agent of Death (Also published as: The Death Squad in 1989 as by Jack Cannon)1974
Night of the Phoenix (Also published in 1989 as by Jack Cannon)1975
The Smack Man (Also published in 1989 as by Jack Cannon)1975
The Cannibal (Also published in 1989 as by Jack Cannon)1975
The Quest1975
Hitler's Children (As 'Kurt Ladner')1976
Killer Sharks: The Real Story (As 'Brad Matthews')1977
By the Rivers of Babylon1978
Mayday (with Thomas Block)1979
Cathedral1981
The Talbot Odyssey1984
Word of Honor1985
The Charm School1988
The Sniper (As by Jack Cannon)1989
The Hammer of God (As by Jack Cannon)1988
The Death Squad (As by Jack Cannon)(same as The Agent of Death (1974))1988
Night of the Phoenix (As by Jack Cannon)1988
The Smack Man (As by Jack Cannon)1988
The Cannibal (As by Jack Cannon)1988
The Gold Coast1990
The General's Daughter1992
Spencerville1994
Plum Island1997
The Lion's Game2000
Up Country2002
Night Fall2004
Wild Fire2006
The Gate House2008
The Lion2010
The Panther2012
The Quest (rewritten en extended version of the 1975 novel)2013
Radiant Angel (UK Title: A Quiet End [2015])2015
The Cuban Affair2017
The Deserter (with Alex DeMille)2019
The MazeDue October 2022