Brown was part of the Bay Area figurative movement and is one of the most important of that crew. Her first major show was at the Whitney Museum's yearly show in 1960. She was 22 years old in 1960. Saying this is unusual for the time is a massive understatement (both in terms of age and gender).
Her art is obviously figurative, as one would expect a person from the figurative movement, but her colors are unique. They are bright, veering sometime into pastel. Some pieces seem to be inspiration for a number of experimental comic/graphic novel artists of later years (not super hero comics). Her works are rife with personal symbolism as well and you have to do some research to decode them. It is always a thrill to see Brown's paintings.
You can find out more at the Joan Brown Estate website. Her family started this in 1990. It is a wonderful collection of images and information.