I love the illustrations in Witches, Pumpkins, and Grinning Ghosts
-- you can tell they were drawn in the 70s, in a charming way -- but the writing style is too choppy and random for me to enjoy.
I like that a children's book includes info about actual witches, Druids, celebrations of the dead, etc., and I liked the background provided for jack o'lanterns, bobbing for apples . . . all those classic games and symbols associated with Halloween. I haven't gone through the book chapter-by-chapter to fact-check, but I suspect some facts might be a little jumbled; some bits just SOUND wrong, but I can't back that up.
Most of my problem, though, stems from Barth's writing style; the book reads like a grade-school essay, with info just dropped into each chapter randomly, with no smooth transitions between time periods or subjects. It's hard to read, or maybe just hard to focus on. It's not a book I'd recommend unless you really dig the art.