I was thinking of a duology I read years ago (mid 2000s maybe). It was set on an Earth where Venus and Mars were the way 1800s scifi writers thought of them. Venus was Swampy and filled with Dinosaurs. Mars had an ancient dying civilization. One book was on Venus the second on Mars.
I thought they were by Bruce Sterling but I looked at a list of his works and didn’t see them. Does this ring a bell with anyone? Thanks.
“Lords of Creation”
Trilogy
S. M. Stirling
Yes! Thank you! My memory was close. I don’t think I knew there was a third book.
It sounds a little like S. M. Stirling’s “The Lords of Creation” which consists of two novels: The Sky People, set on Venus, and In the Courts of the Crimson Kings, set on Mars. (There was also a short story, “Swords of Zar-Tu-Kan”, which was a prequel to the latter book). I’ve read the first but not the second; but it sounds like it might match somewhat like you describe. They were published in 2006 and 2008.
Ninja’d because I took the time to dig out my copies.
Missed it by that much! 
Now I’m curious. Are they worth reading? Or just time-passing fluff?
I remember liking the first one. I don’t remember anything about the second one. I was looking to reread them but I lost my copies in a move so I may rebuy them.
Looks like it was Kismet I asked about this because the third book is due out in May of next year (a long time for a follow up).