Off the Rails is the second book in the Border Patrol Series by Jill Sorenson, and in my opinion you really should read the first book Caught in the Act that way you have the backstory of how Ian and Maria met and what happened while they were together before the beginning of this book....which I unfortunately hadn't. That being said I was able to follow along without a problem but I think having the back story would have given me more as far as the characters relationship and the chemistry between them.
Most of this book took place while riding on "La Bestia" which is a freight train that travels along the coast of Mexico from its southernmost border with Guatemala north to the United States boarder. It was risky and things don't go as easy as either one had hoped it would.
Maria had entered the US illegally and somehow got tangled up with the Mexican cartel which is how Ian get re-connected with her. Ian is an undercover ICE agent on the trail of a criminal that Maria has ties with and he's hoping that she will lead him to the man in question. Though neither of them can deny the connection they once had and the chemistry that hasn't faltered in the four years they have been apart, he is there to do a job and that is his main focus.
I liked the chemistry between Maria and Ian and again I think I would have felt more connected to them if I had read the first book, that being said I do plan on going back and reading Caught in the Act at some point in the not to distant future.
***I voluntarily reviewed an Advance Reader Copy of this book
that I requested from Random House Publishing Group - Loveswept through Netgalley*** https://www.netgalley.com/