One Dark Night by Edna Mitchell Preston
This book is old, it looks like it's been around since I was a kid. And yeah, it's from 1969. The format is just like There Was an Old Woman Who Swallowed a Fly, only it's about kids in Halloween costumes. Very cool black, white and blue illustrations. I like the old school pictures, especially of this variety.

Meg and Mog by Helen Nicoll and Jan Pienkowski
Really simple book about what Meg the witch and her cat Mog do one Halloween. Cute story, nice pics.

A Halloween Mask for Monster by Virginia Mueller
A little monster tries on all kinds of different masks--a dog mask, a girl mask, etc.--but they're all too scary. This is a very cute book.