Terry Pratchett and Stephen Baxter - The Long Earth

This book has an amazing premise. What if simultaneous earths suddenly opened up. Worlds which you could step into and colonise. The only thing you could not take with you is metal.
I adore the Discworld but this is quite a different sort of book. Yes it is Science Fiction ,  certainly more that than Fantasy. There are a few flashes of wry humour, I loved the Meatloaf loving nun, but on the whole it is a serious book.
I found it quite hard going until about half way and I assume that it was because when establishing a new series ( I do hope so) you have to lay the foundations and introduce not only lots of worlds but aslo characters.
It is beautifully written and extremely thought provoking, with huge potential for the future, as we begin to see alternative worlds with strange creatures. However, central to it all is the human condition. How will the human race react to this opportunity or challenge?  The introduction of the AI unit Lobsang emphasises this. Will humans ruin these other Earths or will it be sweetness and light, I can't wait for the next installment.