It's simple nbt data. You can find the nbt layout for books here. As for how to manipulate ItemStack nbt, or give players items on world join, or similar, you can use some of the many existing topics on the forums.
The Meaning of Life, the Universe, and Everything.
Hm, I'm trying to make a little info sheet thing for the animals my mod adds in. The mod adds 'exotic' pets, like lizards and hamsters, so I wanted to add 'books' that have all the info about the pets the mod adds. I got the idea from Pet Smart, because they have little info sheets that tell you about the animals you can buy from them. So I might want a custom texture, something simple... Like a piece of paper... I could just do it as a book though...