H.G. Wells wrote War of the Worlds as a warning to the complacent, world-dominating British citizens of his era to not take the status quo for granted. The arrogance of some British politicians in particular rubbed Wells entirely the wrong way, particularly their sentiment that the British had an 'obligation' to 'civilize' the world (read: colonize) for its own good. Well's book was a rock thrown at that attitude-on-a-pedestal, and although he didn't knock it down, he made his point- and in spectacular fashion. In one way, the Martians *were* the conquering British, with their superior weapons and baffling ways that must have seemed incomprehensible to the natives of Africa and other areas colonized by force. Wells' dark tale was also a warning that even the British- despite their firm belief in their world destiny- could be squashed like so many bugs by an indifferent cosmos that didn't give one whit about the British (or anyone else's) false boast of superiority. In the end, though, it's a hopeful book- just as the Martians died off because they weren't biologically suited to live in this world, Wells also foretells the end of the British Empire because the British (alien) way was not the native way of life in the colonies, suggesting that the British wouldn't survive there long; the natives would eventually prevail. And they did. On top of all that, it's rousing entertainment that can be read just for its drama and suspense.
And that's why it's still in print a hundred years later.
-Mark Wakely, author of An Audience for Einstein