Warning: This spoils a bit already, but otherwise it's to hard to explain! Sarah Manning witnesses a suicide. She notices something very strange.. The girl that comitted suicide looks exactly like her.. She decides to assume the identity of this girl. During the first season, she discover that they were clones and there are many more 'sister' clones.
How about the actors?
The leading role is for Tatiana Maslany. Before Orphan Black, she starred in World Without End and Being Erica. For me there weren't a lot of actors that I knew before watching Orphan Black. But maybe that's different for you! Jordan Gavaris plays the role of Felix Dawkins. Before that, he starred in for example Unnatural history and the Sea of Trees. Dylan Bruce plays Paul Dierden. But he's also known for Arrow (Adam Donner) and Heroes Reborn.
Who will like this?
The genre is sci-fi, drama, action. You need to be into sci-fi at least a little to appreciate the cloning storyline. I enjoy the series because it focusses a lot on identity: What makes you you and how does another version of you look like? That's very nice developped in the different 'sisters'. Though I have only season 1 + 2 untill now.
How many seasons?
Season 4 started on april 14th 2016. The series started in 2013.
All the 'sisters' lead back to one actress: Tatiana Maslany. She plays all the clones and does that amazing. It feels like you'r watching different persons, but she plays them all. She's been notimated for, and won, a lot of awards for her role in this series. (She won for example Best Performance by an Actress in a Leading Dramatic Role at Canadian Screen Awards and Best Lead Actress in a Drama Series at the Critics' Choice Television Awards). It's possible that the sci-fi part becomes a bit too much for me. Untill now, I like it. For the other seasons it will be dependent on how the story develops.