The 5-star system is not recommended for all cases.
It has been discussed and covered in many UX and media websites and forums.
Maybe I'm biased, but most authors and buyer I know rate 5-star or none at all...and when someone receives anything short of that, most of the times is 1-star and they feel attacked (and some times it is an attack).
Not to mention that the less ratings someone has, the greater the impact of a bad review.
Wouldn't be more beneficial to switch to a thumbs up/heart system? If you like, mark you like it. Otherwise, don't.
Some studies say this increase the number of ratings too, also reducing the impact of
Anyway, just my 2 cents.