1. In itunes, in the general tab of the preferences of the edit menu, check whether there is a check mark before "Book"; 2. Through the first step, you should be able to see the "Book" item in the itunes database. Select the books to be synchronized in the Explorer and drag them to the "Books" item in itunes; 3. After connecting the ipad, see if "Synchronize Books" is selected; 4. When synchronizing, the books in the database will be synchronized to the ipad.