Underwhelming and disappointing supermarket white bread of a book. A great initial concept with so much potential but the book is a hallmark movie of maudlin, frustratingly safe drama that never really pushes the concept and sticks to societal issue 101 fare. This almost could’ve been a good allegory for a modern societal problem, or a direct exploration of one if the box had revealed something else other than lifespan or changed the person in some way (race? lgbtq+? wealth? class/caste? So many possibilities). The emotions and issues faced in the story certainly are generic enough that you can swap out “short string” with something else in the story and get a similar result, which speaks to how unambitious it is and how much the idea is squandered. Hard to recommend.