A solid 3.5 stars. El-Mohtar and Gladstone pull off an impressive literary conversation with and through their fiction, discussing freedom, duty, and the written word while throwing around sci-fi high concepts at what feels like a rate of more than one per page. This book is fun - The writers are clearly having fun, the characters are having fun, the book sincerely wants you to have fun reading, and if you are a sci fi fan then you probably will. Probably!

There is a slightly uneasy genre blending going on in this book. Not between sci fi and romance, which are and always have been natural companions: if speculative fiction is meant to envision potential ways of living, then love and romance will always be an element of that, even if, in some cases especially if, through its absence (Brave New World, 1984, etc.). What does not quite work for me is the coming together of quite a cutesy form of romance - The central plot is, after all, a time-and-relative-dimensions-spanning meet-cute, which it matches with the wry, self-referential dialogue in the epistolary sections of the novel - and at times quite dry sci-fi concepts. It was a bit like interleaving pages of Foundation through Ready Player One. This will work for some, probably for many, and the overall effect still worked for me as someone who rarely reads either hard sci-fi or straightforward romance, but the mixture certainly feels like an acquired taste.

For all that, it's a great concept, a good story with some likeable characters, and it's short - If the premise has you intrigued then it is very unlikely you will leave disappointed.