@Mesrszmit - The original mod would have to be updated first, but I think I'll wait and see if they add sandbox setting to adjust stuff

Build 42 perhaps?

if the book was read by someone who already had T1 maxed, reading the book would award nothing. Does it give 3x xp speed bonus, or really nothing?

@V.A.Nekrasov - No. For the reasons read the comments below where this question has already been asked, and answered before.

Is there a sandbox setting? Let's say I want books to give only 80% of the first level of the book, and then farm everything with 3x speed. If not, could you add such an option?

As stated in the description, this mod: "provides enough XP for the first tier it covers, and a small amount (approx 15%) for the second tier." The difference is that the original mod would fill both bars. You should be reaching the second tier with appropriate books. The reason why it has to work this way was explained in a comment just below on 30 Jul @ 8:36am 

I checked and Book Learning is no longer in my mod list. I deleted the mod files and restarted the server as well and still get 2 levels with a book. It looks like the #of pages is too high. After the 1st level, the exp multiplier drops but the "pages" meter is only 20% filled. It seems like the exp reduction is happening, but it lets me read long enough to get the 2nd level anyway.

Install this mod instead of the Book Learning mod. You do not need both.

I added this mod after installing the original book learning mod. It seems like this one didn't overwrite that mod. Do you know anything about that? It might be my server, but I made sure both the workshop ID and the Mod ID are correctly showing in the dedicated server's .ini file. When we read the books though, it still gives us 2 levels of the skill (first aid lvl 1 was our test).

@Mesrszmit - Unfortunately, due to how the mod Book Learning works, a sandbox option to tweak the XP amount would not really be viable. Essentially it works the same as vanilla skillbooks, but awards XP for the associated levels. Awarding any less than enough XP to fully cover one of those levels, and at least 1XP more would result in the mod acting very janky.

For example:

If skillbook 1 offered only enough XP to get Tier 1 to halfway, reading it at T1 would give half the XP required for T1, but if the book was read by someone who already had T1 maxed, reading the book would award nothing.

This is one of the reasons why I made my other skillbook mod

Bro that's EXACTLY the mod I was looking for, TYSM man. And also it would be nice to have a sandbox option for how much XP it gives if that's possible.

I made this mod coz the original almost provided what I was looking for in an alternative to vanilla skill book progression, but it still did not sit well with me as it did nothing with redundant skill books.

So I made this other mod: https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=3291799176