A while ago, I ran across a post about 0th level spells - cheap spells for poor or untalented spellcasters. As a natural gnomish trickster (as both character and temperament), I decided to take a stab at what gnomes would do with similar low-level magic, and the result is both humorous and terrible.
I don't have the price for the spellbooks, but I assume it would be fairly inexpensive, compared to other spellbooks containing spells. I also assume that most mage types wouldn't be caught dead with a book like that, and many deities would be most displeased if a follower tried to use one. Various dour types may not be able to use joke spells at all, since they don't have enough humor to power the spells.
Deep Carbon Observatory has a room describing spells known by slaves that are hilariously tragic. spells like "Reduce Scars" "Minimise Thirst" and "Hide Sorrow"
This is one of my favorite house rule additions of all time. And I say this as a humorless curmudgeon who had no tolerance for gnomes until demanded by a backer. When the time is right I would love to include this in AXIOMS.
I also think you're on to something with regards to 0.5 spell points being a useful demarcation for 0 level spells. I could see the Prestidigation proficiency being replaced with an opportunity to know some X number of 0th level spells which can be cast at will or some such.
I nearly panicked when the link to your Joke Spells 404’ed, but I found the PDF. (I believe you can edit the first post of a thread you open, if you’d like to fix the link.)
As far as I know, you’re the first person to apply my 0th level spell rules to create new spells