This is book 2 of the "Barsoom" series.

This note contains spoilers for the book.

 

John Carter dies on Earth again, and shows up back on Mars.

He turns up in the polar regions, where there's an actual ocean. Unfortunately this is the domain of Issus, the goddess of Mars, who turns out to be a total fraud. There's an outer circle, and then the inner circle, with their own Martian races. This is all detritus from the long decline of the planet; apparently those particular species chose to just become more and more competitive, rather than finding a way to work together against their huge problems.

First he has to survive and get out himself, then he discovers that Dejah Thoris has gone down the river to there (the primary alternative to dying in battale, apparently), so he has to go rescue her.

All sorts of hairy adventures, stumbling across his son (we won't talk about the fertility of a humand and an egg-laying Martian; after all, we don't know how he got there, or what changes might have been made along the way, though Carter never mentions noticing any).

The tradition is that anybody coming back from the domain of Issus is to be killed. The Therns have priests undercover everywhere and encourage this. Because it's all a fraud, and they need a steady stream of victims to keep it going.

It's interesting that the whole plot is about how religion is totally a fraud for the benefit of the priests. On Mars, I mean; there's no mention of Earthly religion that I can recall at all (though, when you think about it, a Virginia gentleman of the period would probably have had some religious convictions). It's amazing what science fiction and fantasy can get away with sometimes!

At the end, Carter doesn't die, for a change. He does, however, see Dejah Thoris disappear into the hugely complex moving labyrinth that Issus runs, with a friend and an enemy, and not enough food for the cycle until that chamber opens again. His men bring and throw in food at the last second, and the enemy kills somebody (we don't know who), which reduces demand and my (by Martian standards) provide more food too. So, in a year, that chamber will be open again, and possibly somebody will still be alive.

I'm bothered that technology has fallen so low that they can't block the thing, or break it open, or stop it. They're good at breaking things, in general!

Since he's not dead, perhaps he'll proceed to have adventures while waiting that year. There are still issues with the rule that returnees will be killed, I think.