You CAN re-divide up your book–enter it in, making “lessons” or “readings” instead of chapters, and just specify the pages you want. I find that very, very tedious. So I myself just use the chapter divisions, and then I put a sticky in the front of the book saying “Read TWO chapters a week” or “Read 8 pages a week” and they can just enter “worked on” if they did not complete a whole chapter, or they can just enter that they are done with a chapter when they are done. Does that make sense? I find it a lot easier on me, personally. I don’t like to enter in a book with a gazillion new divisions if it is already there for me in chapters!