Monster, 91 Days Recommendations
Both have the same dark-ish feel to them and distinct beautiful art.
Both are about clever plots created by exceptionally sharp characters and are quite deeper and complex than one might think at the beginning.
Both are loaded with action, drama and thrills must-see's.
While Monster's plot is much deeper and more developed and complex, 91 days' plot is developed to the best extent 12 episodes allow.