Each book can be read as a standalone novel, but to have the series experience, the following order is suggested. 

Order of Titus Ray Thriller Series:

One Step Back, the prequel to One Night in Tehran

One Night in Tehran, Book I

Two Days in Caracas, Book II

Three Weeks in Washington, Book III

Four Months in Cuba, Book IV

Five Years in Yemen, Book V

Two Steps Forward, Book VI

Three Steps Away, Book VII 

Four Steps Missed, Book VIII

Five Steps Beyond, Book IX

One Good Time, Book X 

Two Good Deeds, Book XI (Coming 2025)

Order of Ben Mitchell/Titus Ray Thriller Series:
(These novels are in the voice of Titus Ray, but Ben Mitchell is also featured.)

Ben in Love, Book I—chronologically, this book follows Two Steps Forward

Ben in Charge, Book II—chronologically, this book follows Three Steps Away

Ben in Trouble, Book III—chronologically, this book follows Four Steps Missed

Order of the Mylas Grey Mystery Series:

A Day Ago, the prequel to One Day Gone

One Day Gone, Book I

Two Days Taken, Book II 

Three Days Clueless, Book III

Four Days Famous, Book IV

Five Days Lost, Book V

Six Days Spent, Book VI

Seven Days Off, Book VII (Coming  2024)

Order of the Silas McKay Suspense Series: 

One Wonders, Book I 

Two Believe, Book II 

Three Confess, Book III

Four Doubt, Book IV (Coming 2024)