Countdown Zero (Agent Zero Spy Thriller #18)

Countdown Zero (Agent Zero Spy Thriller #18) by Jack Mars is out now, published January 24, 2026.
Countdown Zero (Agent Zero Spy Thriller #18)

Author: Jack Mars

Published

Published: January 24, 2026

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Countdown Zero (Agent Zero Spy Thriller #18) Release Date: January 24, 2026
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‘You will not sleep until you are finished with AGENT ZERO. A superb job creating a set of characters who are fully developed and very much enjoyable. The description of the action scenes transport us into a reality that is almost like sitting in a movie theater with surround sound and 3D (it would make an incredible Hollywood movie). I can hardly wait for the sequel.’
–Roberto Mattos, Books and Movie Reviews

COUNTDOWN ZERO is book #18 in the #1 bestselling AGENT ZERO series, from #1 bestselling and USA Today bestselling author Jack Mars (with over 10,000 five-star reviews). The series begins with AGENT ZERO (Book #1), a free download.

Beneath the ocean’s surface lurks a submarine gone rogue, threatening coastal chaos with hypersonic missiles unless their ransom demands are met.

With only 24 hours to halt the countdown to devastation, Agent Zero must navigate a deadly game of cat and mouse beneath the waves—a game where one wrong move could lead to catastrophic consequences.

The AGENT ZERO saga offers a gripping journey packed with unexpected turns and dynamic action, keeping you enthralled from start to finish. At the core of this thrilling series is an engrossing relationship between a father and his daughter, which is sure to keep you reading voraciously until the early hours.

Books #19–#24 in the series are also available!

‘Thriller writing at its best.’
–Midwest Book Review (Any Means Necessary)
⭐⭐⭐⭐⭐

‘Thriller enthusiasts who relish the precise execution of an international thriller, but who seek the psychological depth and believability of a protagonist who simultaneously fields professional and personal life challenges, will find this a gripping story that’s hard to put down.’
–Midwest Book Review, Diane Donovan (regarding Any Means Necessary)
⭐⭐⭐⭐⭐

‘One of the best thrillers I have read this year. The plot is intelligent and will keep you hooked from the beginning. The author did a superb job creating a set of characters who are fully developed and very much enjoyable. I can hardly wait for the sequel.’
–Books and Movie Reviews, Roberto Mattos (re Any Means Necessary)
⭐⭐⭐⭐⭐

Excitement Rating
[Average Rating: 4]

Genre: Thriller

Jack Mars

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Excitement Rating
[Average Rating: 4]

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