It seems like "collectible" Coloring Book is almost a contradiction in terms. If used as intended, that would immediately destroy it's value. (Unless Picasso was doing the doodling!) The same criteria might be used for collectors of crossword puzzles and the like. But, as long as it's bought, never used and there's an attic in the house, there will be collectors!

Actually, coloring books are a hot new field just now being discovered by many collectors. Below is a link to a book which includes 500 full color photographs of coloring books published during the last 100 years. Also included is a history of coloring books, plus information regarding the subjects of each of the books: TV, movies, personalities, dolls, paper dolls, advertising, comics, cartoons, Disney and history.