This is specifically only for "entertainment" (boredom/stress reducing) VHS and books btw, not skill giving ones.
So currently the way non-skill VHS work is (afaik): you watch it, upon which you get stats from it (-boredom usually) and afterwards you get nothing from watching it again. Suggestion:
Instead of getting nothing when rewatching, upon watching a specific VHS , it instead becomes "spoiled" in training materials database (tracks last time you watched it, instead of only whether you did or not) and slowly unspoils over time (ex. over a month+, more? idk the exact balance) and while it is spoiled, the stats it gives from watching again are reduced from original stats based on current spoil level to original stats it gave instead of permanent flat zero, which means if you got ex. -100 boredom from watching a specific VHS first time, rewatching it immediately afterwards gives 0 boredom, same as currently, watching it a day later gives maybe -1 boredom and waiting for a few weeks gives -20 boredom from rewatching, once it fully unspoils you get -100 boredom from watching that specific VHS again, as the first time (maybe it should be less than 100% of original, like 80%, as "you already know the plot", maybe relevant). This is so the player can't just get a few VHS and get permanent anti boredom system through replayability but rather needs to seek out diversity, VHS stores may need rebalanced loot tables for non-skill VHS like those as a result, so you can't get all VHS you need from a single one.
Same system for books: instead of all books giving identical flat stats and getting consumed upon reading, books starting with random titles similar to VHS (extra opportunity to include references like with VHS, but at least different IDs are needed) and give different stats based on that (boredom reduction, stress reduction, etc, can be random as it doesn't effect skill progression to need predefined ones like skill books/skill VHS and is more food-like-rng) and reading does not consume the book, rather puts it in a "spoiled" state in training materials database that also obviously would need to track individual books (titles) like it does VHS. Books should also maybe take longer to get the same effect from them compared to VHS considering reading is slower than watching, or have more profound effect (they kinda already do due to stress reduction which afaik VHS don't give).
Comic books and magazines obviously can work the same as above, with unique titles or at least IDs, and crossword/wordsearch puzzles are obviously one and done as currently but can be faster and stronger effect as compensation for being single use, still should be tracked per player instead of consumed on use though, nothing is stopping another player from solving the same puzzle someone else did (other than the fact it is written over, maybe another use for eraser/pencil combo to be able to "read" those?) so I suggest they work like current recipe magazines do where player can read it and then another player can read it as well, all this would obviously need massive player-based database use though (john zomboid comic book #3:last read 2 days ago, wordsearch puzzle #5: read) so not sure how performance/filesize friendly this suggestion is.
Suggested UI for players to be able to keep track of this: each book/VHS showing "last watched x days ago, effect efficiency x%".
Reason: turning literature and movies/CDs into a "food for thought" system, where player can build a library of art to keep their mind intact and inspired with zombies roaming around the desolate cities.
Probably not needed with the current mechanics but if in future the player character will need/want "to live, not just survive" such as example passively increasing dullness moodle (not boredom) from specifically not consuming any literature/movies or received any other "mind nurturing experiences" for a while that eventually leads to unhappiness or other negatives, ik it sounds like "another food bar to keep filling" which is why it should be more of a long term slowly acting thing in comparison, boredom/unhappiness alone as is doesn't cut it to necessitate a system like this obviously.