I don't know exactly how you would want to use these, but if you mainly need a way to look at a certain list of books, have you considered using Resource Lists? You can create them in the sidebar of the resources view, give them a name, and then drag resources in. If you need to actually record when they read the book, we don't currently have much related to that, but you could always record it in the notes field for the book. Not an ideal solution, but combining the two of those might be enough.
An alternative to resource lists is resource categories. Drag one resource onto another to create a category, these are generally more fixed divisions though, and you can only put a resource into one category (although they can be nested) so it might not work as well for this case.