The Beast and the Bethany by Jack Meggitt-Phillips
Illustrated by Isabelle Follath
Ebenezer Tweezer is a youthful 511-year-old. He keeps a beast in the attic of his mansion, who he feeds all manner of things (including performing monkeys, his pet cat and the occasional cactus) and in return the beast vomits out presents for Ebenezer, as well as potions which keep him young and beautiful.
But the beast grows ever greedier, and soon only a nice, juicy child will do. So when Ebenezer encounters orphan Bethany, it seems like (everlasting) life will go on as normal. But Bethany is not your average orphan ...