The story is set in an old Western-style hospital where Takumi was confined after he was in an accident. Since then Takumi has experienced an odd condition where he can see the "deep voices" of the past events bound in different parts of the hospital. He seems to be able to also slip into other people's consciousness while being asleep. Together with Amano Aki, a journalist, he wants to investigate about the mysterious past of the hospital.

What is a good anime to recommend for someone who barely watches it?

Since you liked OPM, I’ll give you a couple of action anime which are short, but have great animation and well choreographed fights: Samurai Champloo - Out of the two, this one definitely has more comedy and made me laugh quite a lot (and I’m not the easiest for laughs).
The villains are great and there are a few twists here and there… the plot overall isn’t complex, but very engaging nonetheless.
Thoroughly enjoyable. Afro Samurai - It’s a pretty serious series but there is one funny character who made me LOL at times, just because of his personality and English voice actor.
It’s got a great feel! You don’t have to be a full-on anime fan to enjoy these, just someone who enjoys action shows.
Trust me, they are both well worth the watch and on a scale of recommendation out of 10, I would rate them 1,000,000! (or maybe I should say over 9000)