The Long War by Terry Pratchett & Stephen Baxter

This is actually the 2nd novel in the series, and I haven't read the 1st, so that sometimes makes the novel more mysterious !!!

I love both these authors, and was so excited to read their first collaboration :>)

The premise of this series is that the multi-verse theory is correct, and some people, unbeknownst to even themselves, are natural "steppers" - that is, they can step from 1 universe to another, unaided.

A billionaire - reminding me of Sir Richard Branson - who along with lots of other research he is bankrolling, ended up bankrolling a device that allows people to "step" from 1 universe to another.

So, for the benefit of mankind, this billionaire gives the stepper device free to everyone, and then sets up a fleet of "twains" (named after Mark Twain) that are reminiscent of zeppelins, to help people transverse the mulit-verses, for free.

For instance, if I am standing somewhere in Tulsa OK, and I click my stepper while taking 1 step, I will be in the next multi-verse, in the exact same spot, since all the multi-verses are copies of each other, with usually very small differences...you can only go "east" or "west" (not north or south) stepping, and so if I "step" into the next multi-verse, and then want to go to Utah in that multi-verse, I would have to either walk or take a twain.

At the part of the novel I've read up to, there are thousands of mult-verses, and not an end in sight...

There is a lot of discussion about human and animal rights, economies of "Data Earth" (our original),the "frontier earths, the unexplored earths, etc.

There is 1 multi-verse where a celestial body hit the Earth with such an impact, that it destroyed the Earth.  If you "step" from the one previous into that one, you "step" into outer space  (doesn't explain how they figured that out !!!), but they are utilizing that as a no-gravity space port.