Many book collectors are quite fastidious about what they add to their bookshelves. They only collect pristine texts that are housed in pristine bookbindings that are housed in pristine dustjackets. They will not even consider books that are, in their view, "defaced" by things like bookplates or annotations, even if the bookplates or annotations are much more valuable, from a book history standpoint, than the titles themselves.
Little wonder, then, that one of the most conspicuous successes in publishing history rarely appear on such shelves. We are speaking of activity books.
These often ephemeral titles are defined as books designed to engage the user in a pursuit other than (or in addition to) reading, for example, an instruction manual for science or craft projects, or a volume containing puzzles or word games:
Such books are published for both adults and children, and the topics to which they are devoted say much about the cultures within which they are published:
Consider what book historians might discover about text receptivity, the editorial and marketing decisions of book publishers, and the subjects that a culture deems to be important, all from intense study of an extensive collection of activity books. How have the topics covered by such books changed over the decades? Are some subjects covered more consistently and thoroughly than others? Have some subjects always been taboo for the publishers of such books?
Let's be even more specific. One of the most widely and continuously published types of activity books has been the crossword book. How has publication of these types of books changed over the decades? What does the publication of such books say about the evolution of the languages in which such books are published? What does the publication of such books say about cultural definitions of thorny concepts like "intelligence?" Does the publishing history of such books suggest that publishers, at least, perceive different levels or types of intelligence to which such books might be marketed?
Of course, for such books to be really useful to future book historians it would be helpful if the activity books in one's collection contained numerous examples of reader engagement with such texts:
Therein, of course, lies the rub: very few folks who actually engage with such texts ever save them. Such items are ephemeral -- most folks use them and discard them.
But if future book historians are to have anything to work with, it seems unlikely that they will get much help in this area from institutional libraries -- we are unaware of any libraries that consistently make the acquisition of such books a priority, especially activity books that encourage the reader to mark the books in some fashion. Seems to be a very much overlooked niche for the enterprising book collector....