Grant strove to disabuse herself and her readers of preconceptions, to eschew what she called 'group-think'. She was not interested in blind faith and blind belief, but in what could be perceived as true by the five senses. She claimed to have an unusual gift of "far memory" -- the ability to remember previous lives, and something she referred to as "sensory awareness". She said that she experienced many realities that are not available to most people.
A collection of previously unknown writings by Grant was published as Speaking from the Heart: Ethics, Reincarnation & What it Means to Be Human in 2007 by Overlook Press in the USA and Duckworth Press in the UK. It was edited by her granddaughter Nicola Bennett, with anthologist Jane Lahr and Joan's closest friend Sophia Rosoff. The book contains poetry, essays and a series of lectures she gave at Edgar Cayce's Association for Research and Enlightenment in Virginia Beach. She had a reputation for talking and writing with clear certainty about her belief in other realities, past lives, and death. She said that for her, the veil between the "worlds" simply did not exist.
With her third husband, Denys Kelsey, she wrote Many Lifetimes, in which she explained how she supposedly remembered her own and others' past lives.
She also wrote several children's books which contain stories she claimed she was told in past lives.