Cranberry Christmas by Wende and Harry Devlin, 1976.

Mr. Whiskers normally enjoys Christmas, but this year, he has problems.  To begin with, he can’t go skating on the pond near his house with the children of Cranberryport because his disagreeable neighbor, Cyrus Grape, claims that the pond is actually on his property, not Mr. Whiskers’, and has forbidden the children to set foot on it.  Mr. Whiskers is sure that he’s wrong, but he’s having trouble finding the paperwork to prove that the pond actually belongs to him.

Then, Mr. Whiskers’s sister, Sarah, is coming for Christmas.  She believes that Mr. Whiskers doesn’t take proper care of himself or his house, and she is trying to persuade him to come and live with her.  Mr. Whiskers doesn’t want to do that because he likes his independence.

To help impress Mr. Whiskers’ sister, Maggie and her grandmother help him to fix up his house for Christmas.  In the process, they discover something that helps to settle the question of who really owns the pond.

My favorite part was when Maggie and Mr. Whiskers made Christmas ornaments out of Mr. Whiskers’s seashell collection, which he had been keeping in his bathtub.

In the back of the book, there is a recipe for the cranberry cookies that Maggie makes.  The book is part of a series.