I have the exact same issue as the one from #820
Even with the mod installed all by itself I can only find one skill book in the creative menu. This is the case in 1.16 and 1.17, and I have not configured it to remove the skill books. The book is stamina pillager if that makes any difference.

Update: It seems to be broken in the latest versions.
I was able to get rolling working by using : EpicFightMod-1.16.4-1.1.0

Only mods are:
EpicFightMod-16.5.13
jei-1.16.5-7.7.1.139

Using forge: 36.2.20

Only skill book via give command or jre is

Skill Book
Stamaina Pillager
epicfight:skillbook
NBT: 1 tag(s)
Epic Fight Mod

Closing issue as fixed on 18.5.0.1 - available only for Closed Beta Access users