Dreadful. I was reading the old English translation of the book, which always is a problem because Jules Verne was butchered whenever translated into English. But this only accounts for some of the problems of the story. Verne seems to have tried to write a more funny take on nationalities of Europe, and so we have our hero Hector get whisked away from Algeria by a comet, which coincidentally also took part of the Med with it, including some of the most annoying stereotypes of European nationalities possible. This includes stodgy Brits, lazy Spaniards, and of course the impossibly greedy German Jew.
It is the latter which really leaves a bad taste for a modern reader, the treatment of the only Jewish character is so bad it was already a public issue when it was first published. Think about that.
It doesn't help that the rest of the cast is unlikable and arrogant, the science is dodgy even for the time it was written, and frankly I would have loved to see them all killed off in the end. Verne seems to have originally planned it like that. It's a pity his editor said no to that. It would have made a better ending.