The "War of the Worlds" is over, leaving only an angry Earth...and the wreckage of the Martian invasion.
From that wreckage, mankind decides to develope the means to take the war back to the Martians. Scientists and engineers from around the world gather and – led by Edison himself – create a battlefleet the likes the world has never seen, with its next stop: Mars!

While in the
Worldcon huckster's room in 2006, I ran into a table run by a new publishing company called
Apogee Books. It's apparently specializing in reprints of books related to space (for instance, the
Apollo News Reference Manuals) and old science fiction novels. But not just any old SF novels, stuff that people may have been
hearing about for large numbers of years, but haven't seen for twice that number.
One of those "long heard of but never seen" titles is
Edison's Conquest of Mars, which always gets written up in histories of science fiction as the "sequel" to Wells's
War of the Worlds.
Well, it is and it isn't. Back in the 1890's, copyright was a much iffier thing than now (especially between different countries). So after Wells's book came out in England, a flock of reprints (usually in newspapers) popped up in the U.S.
One of those papers was the
Boston Post, which in 1898 printed
Fighters from Mars – or the Terrible War of the Worlds as it Was Waged in or Near Boston in the Year 1900 (and, yes, that title is
way too long). While the story was ported over more or less intact, like the 1938 radio show – or the 1953 movie after that
1 – where locations were all changed from English ones to more local vistas (New Jersey and L.A., respectively), in the Post reprint/write, obviously, all the action of the story takes place near Boston.
And also obviously the serial was popular, because even as the "Wells" story was wrapping up in February of 1898, the
Post had a sequel ready to go:
Edison's Conquest of Mars, by Garrett P. Serviss.
The plot is fairly simple. Following the events of WotW, Earth realizes that just because the
first wave of Martians died of simple local diseases, doesn't mean that the Martians won't try again – nor fix the problem! Obviously then, the only option is to build up some sort of defense, and by-golly, they've got a planet-
load of abandoned Martian gear to reverse-engineer to do just that...
...and from the title, you just know Edison is going to be one of the primary reverse-engineer's.
In fact, they do so
well at this, that before long Edison and the rest of the world's scientists have got a fleet of working "electric propulsion" spacecraft even better than the Martian's "cannonball" ships
2 and – realizing that the best defense is a good offense – decide to attack Mars first, before they can rebuild their forces for another attack on Earth...
...and, again from the title, you just know they're going to succeed.
Serviss's book is, while "quaint," actually not that bad (if you ignore the ending, anyway...;)). If nothing else, the man appears to have invented a lot of the SF conventions so popular that in later years they ended up being clichés:
Heck, he even comes up with the
Stargate concept of aliens visiting the Egyptians and being their gods about a century ahead of that movie.
It's a fun read and a nice way to see where much of "modern" Science Fiction (for definitions of "modern" that include the 30's and 40's) had its roots. If you don't want an actual hard copy of the book, you can also find it
here at Project Gutenberg...