It is not a thriller. If you go with that perspective, you will find it very underwhelming. It is a brilliant drama, with so many layers in its characters, events and the conclusion that it is truly refreshing after all the overly dramatized clutter you have around murder mysteries. It is not much of a mystery either, or maybe it is. However, it does seem a fairly accurate representation of the deep frustrations that surround attaining justice and closure for such crimes given the incompetency of the very system itself.
All the actors were brilliant, the protagonist in particular was phenomenal. The characters seem to behave as close to real life as one would imagine in such a scenario, and that is exactly what hooks you to this series. You truly root for almost every character in this series except for the obvious few. I know it is almost blasphemy for some, but it somewhat reminds you of 'The Wire'.