Sounds good, Manda - I'll keep an eye out for it. Is the title a nod to Rosemary Sutcliff's Eagle of the Ninth?I'm not sure if I'm allowed to alert you to my own book - but it's not out yet, so few people have seen it...
Rome: The Eagle of the Twelfth starts in Parthia and moves throughout the region as we head towards the loss of the Eagle and the attempt to recover it.
Out in May in Hardback and on Kindle.
Palmyra was a significant link between Rome and the Parthians, and there are several novels set around rebellions in Palmyra- Simon Scarrow's Centurion and Nick Brown's Siege: Agent of Rome are a couple that come to mind.
Everyone probably already knows about Jona Lendering's Livius website, but if not, it's a wonderful ancient history resource and particularly useful on Persia/Parthia and anything to do with Alexander the Great.