I started this series with the second book. I had picked it up for two reasons: 1) it sounded interesting and 2) the main character shares my son's name. I enjoyed it so much that I sought out the rest of the Sigma Force books.
Sandstorm is the first of the Sigma Force novels. I was disappointed at first when I discovered that Grayson Pierce was not even a minor character, however, I quickly warmed to Painter Crowe. The story is that of a lost city in Oman. The action was consistent and the history interesting. As with all the books of this sort, there were an obscene number of "well, isn't that convenient" circumstances.
The scenery was amazing. You'd think that endless sands would become boring, but Rollins kept the land alive and moving. Each location was described with enough detail to allow me to form complete pictures in my head. The characters were realistic and vivid for the most part. Clay bothered me. He seemed very on-again-off-again, but he wasn't exactly a main player.
I've enjoyed everything I've read by this author (including the fantasy he writes under the name of James Clemens) and would recommend this book without hesitation. In fact, I've already gotten several family members interested in it. If you like well planned and fleshed out history-mysteries, you'll enjoy this book as well.