It is one for the head (everything you wanted to know about quantum mechanics, astro-physics and relativity but were afraid to ask) but also aims for the heart too. Although, it's the human storytelling dimension that feels the most uncomfortable, with the connections between key characters being curiously under-drawn.
In a way, this is a movie about searching: Mud is searching for his girl, Juniper, and an escape route. Ellis is searching for a model of a functional relationship that the troubled twosome can never live up to. Ellis's real father is searching for a way to connect with his son. It's also a meditation on fatherhood and how hard it can be for dads and sons to communicate.
Sometimes a story comes along that any self-respecting studio exec would throw out for being ridiculous, far-fetched, too unlikely to be believed. Except when it happens to be true. 'Bernie' is such a story, a tale so thought-provoking, bizarre and completely entertaining that the combined star wattage of Jack Black, Matthew McConaughey and Shirley MacLaine cannot outshine it.