Wow, I'm tremendously excited for this. Been a fan of Gullivar Jones ever since the 1970s Marvel CREATURES ON THE LOOSE series, which caused me to go out and find the paperback novel.

Creatures On the Loose #21 - Steranko cover...............................Ace Books
Gulliver of Mars paperback art by Frazetta
Gullivar Jones was published in 1905, and thus preceded Burroughs' first John Carter novel of 1912. But Gullivar Jones makes his trip to Mars in the present (of 1905), whereas John Carter's story begins in the past when he's transported to Mars shortly after the Civil War. So did Carter get to Mars before Jones? Or did they both travel in time as well as space? I'm interested to find out. It would seem explanations are in order to account for the discrepancies between Edwin Arnold's depiction of Mars and Burroughs' Barsoom. Parallel worlds? Separated by eons of time? I suppose there could yet exist unexplored regions of Mars populated by races (the Hither and Thither folk) unknown to the red and green men of Barsoom...
The article mentions that both Carter and Jones are southern soldiers, but the novel describes Jones as a Navy lieutenant who makes his home in New York (although he does have a sweetheart in Carolina), from which point he makes his trip to Mars, via a magic flying Turkish rug.