Sometimes i am forced to change stuff in the mod that forces the game to reset certain values back to default
The first good example of this was when B42 introduced Minutes per Skill Book Page as a vanilla sandbox setting, which made this mod's Minutes per page setting absolete.
There is nothing i can do about this but you won't have to start a new game because the fix is pretty simple:

Use DEBUG mode (or a mod) to change your savegame's sandbox settings.
(Starting a new game also works, but that would be overkill right?)

How do i enable debug mode?

To enable debug mode:
- Rightclick on Project Zomboid in your Steam Library
- Click on Properties
- In the box under Launch Options type: -debug

- Launch Project Zomboid and load your save.
- Click on the WASP looking icon on the left side of the screen, this is the DEBUG MENU.
- Click on Sandbox Settings

If you want ALL reading to go faster:
- Click on the Character tab and look for Minutes per skill book page
- Lower it's value to make reading go faster.

If you only want reading to go faster when sitting:
- Click on the M-13's Reading Tweaks tab and look for Sitting Multiplier
- The higher this number, the faster you read when sitting on the ground or on furniture.

After you are done changing values click Apply Changes
If you want to disable DEBUG MODE, close your game and remove -debug from the launch options.
The settings you changed will only take effect AFTER you reloaded your save game.