[this is in singleplayer]

i've read one of the Passive skillbooks (Fitness 5 specifically), and it applied the multiplier. however when i stopped playing and loaded my save again, the multiplier had disappeared yet the book was still read (380/380 pages). re-reading it just instantly closes the book and does nothing as expected.

i tried reading the vanilla books as well as a non-passive modded book (Maintenance) to see if they did the same. both the vanilla books and the non-passive modded books keep their multiplier on restart.

so it seems something's wrong with fitness and strength keeping their multiplies from skillbooks after reloading a save.

@montoora
I tested it again with all my skillbooks, even after more than 10 minutes the multiplier hasn't disappeared, even after reloading the game the multiplier hasn't disappeared.
Have specially tested the Passive Skillbooks several times and the multiplier hasn't disappeared.
Maybe you use mods that are incompatible, because I only use the existing structure of Zomboid itself for the Skillbooks.
It's normal for a book to close if you've already read it.

weird. and yeah i know it's vanilla for the books to close, i only tested it to see if it would give me the multiplier back after doing so just in case.

i'll have a look through to see if i can figure out which mod's causing it later on.

I am having exact same Issue.

same issue read strong and fitness books quit and loaded my game and they were gone

After your posts, I tested the complete Mod again on SP & MP to find your issues, but it works fine for me.

It sounds to me like some sort of weird mod incompatibility, try running my mod only and see if you still have the issue.

To find the mod incompatibility can be hard, it gives so many Mods for Zomboid, one way is activating my mod and step by step activate other mods.
Or test it specially with mods they're changing anything on Books (Skill books).

thank you for checking will post if I find the mod :)

I'm getting the same issues with the multipliers going away on fully read fitness/strength books. Is there any way yall can think of that we can just dump our active mods on a paste bin or something and then see which ones are active across all players having this issue maybe?

based on bug reports from another mod its probability dynamic traits mod causing it, would test it but i'm having really good run in my current save and don't want to jinx it :)
will test it if and when my char dies

If you guys have the Dynamic Traits mod, that's what is most likely causing it. I posted in the discussions tab on this mod a way to fix it.

I think also more traits or other xp modification mods will cause this issue, in my save game with more traits and others activated, i also have this issue, but in a normal base game trait (car mechaniks and trapping) also after the bonus disappeared i hat negative xp ~ -10 or so. So i assume it has nothing to do with this mod.