Quoting from the original post:

Now in my application I want to include a search function which will find me the book(s) written by more than one author: "Give me the list of books written by Jones AND Smith". 'Jones' and 'Smith' being co-authors for these books as it were.

Using IN on my example table will return lots of books that were not written by both, 'Smith' and 'Jones'. It will return all books co-authored by the two, but it will also return books written by only one of them.