The select I used may be the same as yours (I didn't look at yours vey closely).
The resultset will return one of each author for each book they wrote and one of each book with its' associated authors. It will not return any duplicate row with the same book AND author, which (I think) should be your only concern, no?
If I'm off-track from what you need this for (which I probably am) let me know in greater detail of how you will display or use the resultset.