Patients are being prescribed books instead of pills in the first project of its kind in Britain.
The books are available at Cardiff central library
People who visit their GPs in Cardiff are being recommended books, which they can then borrow from any library in the city.
The "books on prescription" scheme is for patients with a range of mental health problems, and the book lists are designed to help them get better.
It is hoped that the project will be adopted by doctors across the UK.
The scheme was created by Dr Neil Frude, a clinical psychologist who works for the psychology and counselling service of Cardiff and Vale NHS Trust.
It was developed in partnership with Cardiff's library service and local doctors.
The GPs have a book list which covers issues like stress, low self-esteem, anxiety, depression, anger and eating disorders.
They can fill out a special prescription for a book which they think would benefit a patient.
The patient can then take the prescription to any library in the city where the books are stocked.
Dr Frude said it was a simple and cheap way of passing on information to people with mental illnesses.
"Most people see their GPs, whatever problems they have, and this is a way of letting patients know that the books are available to them," he said.
"It's very easy for a GP to prescribe medication, but not other forms of therapy.
"Some people don't want to take tablets, they don't see it as the answer, and this is an alternative."
Graham Cox, 41, from Cardiff, said if the scheme had been around when he was younger, it would have made a huge difference.
"I've suffered from depression all my life," he said.
Graham Cox has suffered from depression since he was a child
"My daughter was still-born, I was assaulted, threatened, my marriage ended and I just went over the edge.
"I was told to take medication but didn't know why.
"If I'd been given the chance to help myself from the beginning, I don't think things would have got so bad."
GP Jacqueline Gantley has been using the scheme at her practice on North Road in Cardiff - she said it was an excellent idea.
"The great beauty about it is that the books have been evaluated by experts, and that gives me the confidence to prescribe them," she said.
"I've prescribed the books to 12 of my patients so far and they're very happy with the scheme, especially after the bad press coverage about certain medications used to deal with mental illness recently.
"They are reassured by it."
Dr Frude and his colleagues will be carrying out a study in a year's time in order to measure the success of the scheme.