Hi Sa Ku,
So far as I know, you cannot add any other activities to a book. What you CAN do is create a link on a book page, that takes you to an activity.
For instance, in your book on any given page, you could add a link that would go to an activity, such as Hot Question, to rate the page. The link could be set to open in a new window. In the description of the Hot Question, just in case, you could then have a link to take users back to the correct page of the book.
I suspect, that whatever method you decide on, it will take a bit of extra work to set it up and get it going the way you want it to.