Fictional Fans

I got silly on discord, so I propose a new soulmark trope: your soulmark is your favorite book (called bookmarks). So, naturally, these change all the damn time, sometimes multiple times per day.

Dating sites that try to pair people with compatible favorite books, and the ones who are like "eh, we'll match the one with the cookbook and the cannibalistic murder mystery, what could go wrong". And the horrible nature of high school english, someone ends up with a bookmark that just says "any book but great expectations" and it stays that way for 30 years.