This Side of Salvation by Jeri Smith-Ready

Everyone mourns differently. When his older brother was killed, David got angry. As in, fist-meets-someone-else’s-face furious. But his parents? They got religious. David’s still figuring out his relationship with a higher power, but there’s one thing he does know for sure: The closer he gets to new-girl Bailey, the better, brighter, happier, more he feels.

Then his parents start cutting all their worldly ties in to prepare for the Rush, the divine moment when the faithful will be whisked off to Heaven…and they want David to do the same. David’s torn. There’s a big difference between living in the moment and giving up his best friend, varsity baseball, and Bailey—especially Bailey—in hope of salvation.

But when he comes home late from prom, and late for the Rush, to find that his parents have vanished, David is in more trouble than he ever could have imagined...