Please tell me what those books are exactly. Do they reset only 2 skills? or your entire points? Or maybe here you can buy 2 of these books with some amount of point reset? I am confused. halp
(as i know there are also other kinds (like other colours), and what is the difference?)

the green one of your pic is a master reset book that removes all the sps, and yes there are brown books that only resets 2 sps

Brown books reset 1 sp not 2.

On topic I'm not sure what the 2 indicates in that maybe there is some sort of buy 2 for this price. Not sure though

It removes all Skill Point as Radon-Ulzer said before.

thank u very much for answers, that will be rly helful.

how do i get one of those books

Go to AH, they are very expensive