Almost any books by Alistair MacLean. They are well-written, exciting and free from sexual themes.
1) Ice Station Zebra (there is a movie staring Rock Hudson and Ernest Borgnie) this is a spy novel about a stolen satelite camera that falls to earth in the Antartic
2) Where Eagles Dare (there is also a movie staring Richard Burton and Clint Eastwood), A world War II drama about identifing spies behind enemy lines
3) When Eight Bells Toll is a story about a police undercover agent catching smugglers who have a hold of terror among the local fisherman.
4) The Guns of Navarrone (Also with a movie staring Gregory Peck & David Niven) is about a group of allied soldiers who have to take out artillery guns behind enemy lines so ships can get in to rescue stranded soldiers.
5) Circus: is about undercover agents who go behind the Iron Curtain as circus performers.
All of these books are obtainable from the library and some may be available as e-books.