The Poison Belt is very much an example of a contemporary subgenre of proto-sf; people at the time were obsessed with mass apocalyptic events, especially ones caused by astronomical objects. It's also very much a weak example of it though, thanks to the soft-pedaled ending! Give me The Purple Cloud any day. But I think it's entertaining enough up until that point.Inspired by this thread, I've just finished reading The Lost World and The Poison Belt for the first time. I thought TLW was a lot of fun and quite well-written, but TPB was much less successful (and it seems like Doyle was already becoming occupied with thoughts about mortality and the afterlife when he wrote it). Now I'm debating whether I'm enough of a completist to read The Land of Mist out of morbid curiosity. There are also the two short stories that were written last, but that Wikipedia's "biography" of Challenger places before TLoM, so I may read them first.
The Land of Mist is the worst kind of bad, though, bad boring. Challenger isn't even in it very much; it's much more about the tedious and sanctimonious spiritualists.
The shorts aren't great but they're short. They read like Golden Age sf stories: a scientific idea made into a story, but not an interesting story or a well told one.