Just finished the latest in the Forgotten Legion series - The Silver Eagle by Ben Kane.
The story covers Roman troops captured at Carrhae who are enlisted by the Parthians as border troops. There is a parallel story covering the sister of one of the leading characters back in Rome. The backdrop is Caesar and the Roman civil war.
This is well researched historical fiction with lots of detail about Roman life and the legions. A storyline that is both interesting and credible - just. Recommended.