A new PlayStation Store update has introduced ratings, a five-star system which allows you to share your opinion on a game you've played. You won't be able to type out a massive review, but you can give a star rating to any game in your library.
As pointed out by Push Square, if you head into the PS Store, select "view product" on a game and from there you'll be able to see the current rating. On the next page, you can see a breakdown of the percentage of players that gave it 5-stars, 4-stars, and so on.
It's worth noting you'll only be able to rate a game yourself if it's in your library. This is likely to avoid mass review-bombings. Hopefully in time we can see more additions to this rating system, to see how many hours people have logged, or even get some fully written reviews.
What do you think of this update?