Afaik books give a set amount of XP.
Reading the book will give you XP until the specified level.
If multiple ppl are only getting into the 40s for the bags then it sounds like bad balancing.
IMO books should cost a bit more if the devs want to use books as a bit of a gold sink. Buying a book 2, 3 or 4 times is poor design. Just make it cost 2,3 or 4x as much and take proportionally longer to read as well. The skill takes us to 70 and make that uniform. Easier for players to know instead of trying to guess game mechanics with no clue.
People used to ask if books were bugged in MO1 and people are still asking kinda same sort of stuff...
Wonder when SV will wake up and realise that their books go against the convention of other shit in the game and there is no clue to say we need to buy the SAME FUCKING BOOK twice to read twice... or more times. How do we gamers learn? By having expectations ripped from under their feet. I guess we read the book by eating the damn pages >.< lol
IMO book system needs reworking. I like the idea of learning through books and offline as well. Just needs to make the user experience better with it.