Voice is a above average crime thriller drama with a very good background story, plot and interesting cases.
While watching this drama there is not one dull moment, it always keeps you on your toes. If not the adrenaline rush, its anger or frustration. There is always an emotion.
Each case always has a twist and it's not always what you think and this keeps you more hooked to the show.
The actors in this drama have done a fine job at portraying thier characters. Kim jae wook and jang hyuk especially.
The bgm and osts are pretty nice to hear but I personally felt at times that they didn't match the scenes.
The female characters is actually one of the coolest characters I have ever seen on drama land. she's strong, smart and rational. Her abilities and skills are mind blowing. I really can't wait to watch her again in the next season.

But I feel the opposite about the male lead's character. He was extremely emotional, impulsive and kinda hypocritical. His lines consist of mainly 2 words and he its really hard to hear him swear at every person he meets expect his son. Most of the frustration happened due to his meaningless actions.
Though the overall storyline is solid, the small inconsistencies and plot conveniences are present all through the story.
Still I would say it's worth it. It's entertaining and interesting to watch.