First few episodes are brilliant. Episodes 3+ lose a lot of creditability. Cosette, and Marius' relationship is STILL ridiculously rushed for a series which aims to give more time to things that are brushed over in most versions, to the point that it seems ridiculous and unbelievable. No sympathy or care to Eponine, Cosette or Marius and their love triangle.
The Thenardier couple are great, as is Valjean. But the best performance is David Oyelowo's Javert.
Would recommend watching but if you feel certain things are unbelivable you're probably not wrong.