The author is Stephen Baxter. It's set in Britain in the 1920s. The Martians are making a second attempt - and they've learned from their mistakes.
Let's hope that humans are prepared, and have re-armed with technology developed from Mars. I'm hoping for Zeppelins armed with heat rays...
The publisher's press release is here:
http://www.gollancz.co.uk/2015/12/gollancz-signs-up-sequel-to-the-war-of-the-worlds-from-stephen-baxter/.
(I think the wait for publication is something to do with waiting for the copyright in the original to expire on the previous day.)