The book begins with the death of young man Daniel, the main hero of the book. From here the book looks backward, a little bit, but mainly it looks forward, to her (no, "her" is not a typo ;-) ) adventures on Lethe.
Lethe is the place where [some?] souls end up [temporarily?] when they die. Except that Daniel is not a soul. Jet.
To me, Lethe had a lot in common with the underworld from the Greek mythology. And yet, the book has a very contemporary feel.
I found the conclusion of the book very ... satisfying. I can't be more specific, because I do not want to spoil the book for you.
(reviewed 4 months after purchase)