The Officers' Wives.

Don't laugh. Yes, the sex is lame by 21st century standards, and the book does involve some controversial issues: West Point, marital infidelity, etc.

What I enjoyed was how Fleming attempted to capture the the Nagl-Gentile split as it emerged during the live fire exercises in Korea and Vietnam.

Afterward you can go back to reading The Peloponesian Wars in the original Greek.