Gulliver Of Mars by Edwin L. Arnold
This is by no means "hard SF" - the story begins with the narrator being taken to Mars by what might be called a magic carpet after he utters a wish to go there. However, if you can enjoy a bit of storytelling by a 19th century writer with a talent for weaving a tall tale, you may find it an entertaining joyride. You just have to avoid taking it more seriously than, say, the Hitchhiker's Guide To The Galaxy.
This is a Mars with seas, forests, wide-spread plants and animals, breathable air, an Earth-like climate, etc.
Upon landing on Mars, Gulliver finds himself near a group of people. These Martians are slightly-built, attractive, happy [human] people. Although Gulliver has some trouble telling the men from the women. Since these Martians are such a friendly and caring kind of people, one of them takes Gulliver under her wing. By staring into his eyes and making a mental effort she is able to make Gulliver understand the Martian language in about a minute. That being taken care of, Gulliver begins to try to learn about Mars and its people.
In the area he's landed, it's (sort of) an idyllic society. If you need a boat to travel on the river, you take any convenient boat. And the guy who left it there will just take another one when he needs it. Food and wine are freely available. [Most of] the people are care-free and child-like. Once a year there's a wedding day when every marrying-age person marries someone. Who you get married to is based on a random drawing. They figure it saves them a lot of time, trouble and aggravation. Doing things the easy, passive way is how the people in this area live.
( This is "idyllic" in an old-fashion sort of way, since they have something like a king, and some people are slaves [in a fairy tale kind of way]. )
It turns out, not all Martians are like that. These peaceful people are actually living in the buildings and such of a disappeared civilization. There is a less peaceful society across the sea that comes once a year to collect tribute from these locals. They pay the tribute because the alternative is fighting and other things that involve inconvenience and unpleasantness.
The tribute these other people collect each year includes one woman of their choosing. They pick the woman Gulliver is infatuated with. So he goes off to follow them to their home country to get his woman. On his way he gets help from some other peaceful Martians. They give him good directions to get to his goal, but he makes a mistake and has adventures and meets a series of people. Eventually, he reaches the capital of the kingdom where his woman has been taken.
By this time, the people he meets are treating him as some sort of spirit, which they feel it is wiser to be careful with. The king sets him tasks to perform to prove himself. Meanwhile, an asteroid flies by Mars, causing an extreme heat wave. Within a couple of days people are dying of heat exhaustion and dehydration. And so on.
He manages to bring the woman back to the other country, but after a while the others come intending to get her back and get revenge...
Perhaps, it is just my expectations from living in a faster paced world than the time when this was written, or perhaps it is from having read many more far-ranging SF books. For whatever reason, as I got further into the book I found the storytelling less mesmerizing. The descriptions seemed more verbose, while the plot seemed to progress slowly. This is probably not for those who like the most modern and fast-paced kind of entertainment.