Top elf / by Caleb Huett.

Enhanced descriptions from Syndetics:

The elves can't be kept on shelves in this hilarious middle-grade debut about what happens when Santa opens a contest to find his successor.These elves are off the shelves.Ollie and Celia think they know what the life of an elf is supposed to be like: Make toys. Help Santa. Make more toys. Help Santa. Try out a new ice-cream flavor. Help Santa.But then Santa rocks the North Pole with a surprise announcement! He's decided this is going to be his last year in the Big Red Suit--and instead of letting his oldest son, the unfortunately named Klaus Claus, take over, he's opening up the job to any kid who wants to apply--Claus or elf. The Santa Trials have begun!Ollie and Celia enter the contest, having no idea whatsoever that they'll soon have to squeeze through impossible chimneys, race runaway sleighs, sweet-talk a squad of rowdy reindeer, and consume cruel amounts of cookies and milk. It's both an adventure and a survival test, far beyond what any elf or Claus has been asked to do before. But whoever rises to the top will get a reward even bigger than Christmas . . .