I Love this book !
I was completely Lost in the story , to the point that when I was startled out of it by a passing bus I was confused as to when / where I was and it took several moments for me to remember (?) the words for what I was seeing in front of me. I was blown away by how compelling the story was.
For me, it belongs with The Time Machine. IF time travel were possible this stories premises might be the "How to".