When I was a child, I loved Jules Vernes' novels. My favorite were "L'île mystérieuse" et "Michel Strogoff". I've read them again after a few decades, and I enjoyed them both. "L'île mystérieuse" is the survival adventure of a small and disparate group, but the main theme is how science can dominate nature. The mystery part is better enjoyed if the reader knows a bit of Jules Verne' other books. "Michel Strogoff" is a pure and romantic adventure in Russia, at the time of the Tatar invasions. It was sometimes brutal for a child reader, but I could still remember many scenes thirty years later. Other good novels are "Voyage au centre de la terre", "Vingt-mille lieues sous les mers", "Cinq semaines en ballon", "Le tour du monde en 80 jours", "Les indes noires". I've a few others which I enjoyed at a lesser point.
Also recommended in this reply