Pretty dated now. The author was a patient in England's infamous Broadmoor Hospital for violent mentally ill people for four years in the 1950s-1960s, having been sent there after he attacked some women with a knife. His mental illness was real and scary, but he was also really smart and an awesome PR person and organizer -- the result being that he got involved in a bunch of patient committees (founding the Debating Society and chairing the Escapee Committee) and campaigned, sometimes successfully, for patients' rights.
Thompson says Broadmoor did little to provide treatment, the place was overcrowded, the staff were overwhelmed and some of them clearly unsuited to their positions, and the focus seemed more on maintaining security than anything else. I'm sorry to say that that, apparently, hasn't changed.