The Giant’s Naughty Elf by Landry Hill

Kilgore has been cast off by his family. Isolated to the other side of the mountain. He’s a lonely recluse, filling his days with boredom. A grumpy giant who doesn’t like Christmas.
Until one day, a little elf appears at the mouth of his cave.
Luna’s been warned never to go to the other side of the forest. She’s been told the giants are dangerous. But… she doesn’t listen. She wants to show her appreciation to the ones who guard the North Pole. She wants to thank the giants for protecting Christmas from those who want to steal the magic of the holiday.
But as soon as she finds herself face to chest with one big, surly beast, she realizes she’s made a mistake. Kilgore’s seen something he wants, and he’s not going to let her go.