This example of early science fiction is certainly interesting as a view into the mind of cultured well-educated Victorians. They are violently racist, revelling in genocide to cleanse the world of "inferior races" for its population by white men and their eventual conquest of the universe; they are sickeningly religious and dabble in spiritualism. But in their favour, they seek scientific explanations for everything (even the supposed ascension of Christ is explained (badly) in scientific terms) and don't shrink from engineering. Indeed, the opening section is all about the Terrestrial Axis Straightening Company, which seeks to abolish the curse of seasonal change by pumping water back and forth between the Arctic and Antarctic thus redistributing the mass of the Earth. And if that's not an engineering project I don't know what is!
Of course, a moment with a pocket calculator - or a Victorian slide rule - would demonstrate how utterly absurd such a project is. Much of the other science in the book is similarly silly, including homeopathy, arguing from conclusions, and so on. But there are some fascinating ideas buried in the dross. It's the first popular description I'm aware of of gravitational slingshots, for example, the first description of a practical speed camera, and contains a working explanation of how to find extra-solar planets by occultation of their stars' light. There's also some intriguing speculation about pocket-sized portable stars, almost identical in function and outward form to Asimov's "Foundation" series's atomic lights.
The story itself breaks down broadly into three sections: the first is a rather tiresome introduction to the main characters via their work with the Terrestrial Axis Straightening Co. Second is their journey to and exploration of Jupiter - where their first actions are to test whether the air is breathable by, errm, breathing it, and to find something to shoot. Oh there's lots of things to shoot. Cue a description of parallel evolution, lots of amusing theories, and a good Boys' Own adventure in the wilderness.
And then there's the unfortunate third section. This would have been much better omitted, leaving us with an enjoyable (if not very good) novel. Unfortunately, they find the Christian heaven on Saturn, spend lots of time talking to spirits and wibbling sagely at each other, and generally waste lots of valuable paper in printing their tiresome speculations. There's potentially some interesting thoughts here on the human condition and morality, but they spoil what was up to this point a work of entertainment. And in any case, there's nothing original there, it's all been done better by other authors.
So, worth reading? The first two sections certainly are, provided that you like the sort of silliness that H. G. Wells vomited forth, and provided you can put up with the quite revolting creatures that were upper-class Victorians. But I'd not bother with the last section if I were you.