I got dis for you.
I found it in the WritableBook and EditableBook classes
This is what i had:
ItemStack tomeStack = new ItemStack(Item.writableBook);
NBTTagList bookPages = new NBTTagList("pages");
bookPages.appendTag(new NBTTagString("1", "Insert text here."));
bookPages.appendTag(new NBTTagString("2", "Insert moar text here."));
tomeStack.setTagInfo("pages", bookPages);
tomeStack.setTagInfo("author", new NBTTagString("author", "Author name here"));
tomeStack.setTagInfo("title", new NBTTagString("title", "Title here"));
tomeStack.itemID = Item.writtenBook.itemID;