16 For Ever, by Lance Rubin

When Carter wakes up on the morning of his sixteenth birthday, he's psyched and ready to give his little brother hell.  But he finds his little brother is now older than him, as in fact is the rest of the world.  To him, it may seem like he was fifteen years old yesterday, but six years have gone by since then.  For unknown reasons, Carter is stuck in a loop.  Every year, instead of turning seventeen, he turns sixteen all over again.  And with no memory of the past year, he's forced to relearn everything, aware that time has passed for everyone else and his friends have gotten older.

This is especially hard for Maggie, his girlfriend for most of the past year, whom he no longer even remembers and who is now a year older than him.  If Carter is going to loop every year, what chance does their relationship have?  At first, Maggie tries to keep the fact that they even dated a secret, but that doesn't last long.  And since this is a YA novel, they are pretty much fated to come back together.

All of which leads to the pressing question of why Carter is stuck in his loop in the first place. At first, Carter thinks that there was a mistake that he made somewhere before his seventeenth birthday that triggered this.  But as he and his friends and family dig into the matter, it seems much more complicated.

I liked the premise of the story, but it's a hard idea to pull off.  Not only fantastical, the concept of getting older without growing up raises all sorts of logistical issues (some of the funnier of which, like a high school junior being legally old enough to buy booze, are explored).  Rubin goes down a few rabbit holes trying to logic these out, but the story suffers the harder he tries to explain it.  It works best if we just take the aging thing on faith and run with it.  The rest of the story is fairly average -- entertaining and enjoyable summer reading -- but without much to help it stand out.