I got a few of these. I used it once on a character and get a skill boost. Then if I use the book again on the same character nothing happens. I tried using it in the next chapter, still nothing.

Are these books really meant to be used just once per character or am I missing something?

The first time a given character reads a book, he gets a big skill boost. If that character reads the same book again, there is a small chance (8-20%, depending on the book) to get a small skill boost.

In my opinion, it is really not worth the hassle to try to grind those small boosts from subsequent reads. Just read each book once with each character, making sure to have the relevant skill(s) selected.

Take into account that each skill point (the whole numbers shown in the characters' sheets) is comprised of 256 experience points each, and that reading a book again gains only 100 minus the current skill level experience points when, and only when, you are lucky with the percentage roll corresponding to that book.

So:

1) You will see the skills change only when the char has already accumulated at least 256 experience points in that skill.
2) The higher a skill raises, the less useful it is to read the book again, since it will take more reads to raise it.

Another thing to remember is that the amount you get depends on your skill focus choices. If you have only that skill selected then you will get 50% more than if you did not have that skill selected and had other skills selected.

reading a lot of books can be useful as it speeds up time.
every X days (I think it was 2 weeks) all party members gain +1 health and +1 stamina