A blanket ban on books being sent to prisoners in England and Wales was declared unlawful on Friday in the High Court.
The challenge to Justice Secretary Chris Grayling’s controversial policy was brought by Barbara Gordon-Jones, an inmate with a degree and a doctorate in English literature.
Restrictions on sending books to jails were imposed last year in a shake-up of the system of rewards and punishment designed to make it more difficult for drugs to be smuggled behind bars.
The policy provoked furious opposition with Philip Pullman, Melvyn Bragg and Joanne Harris among the prominent authors to condemn the changes to the Incentives and Earned Privileges Scheme.
His decision was a victory for Gordon-Jones, a 56 year-old convicted arsonist with a borderline personality disorder.
Gordon-Jones, of Tunbridge Wells, Kent, who also suffers from depression and epilepsy, is serving an indefinite sentence at Send prison, Surrey.
She was denied legal aid but was able to bring her court challenge because lawyers represented her for free.
A Prison Service spokeswoman said: “This is a surprising judgment. There never was a specific ban on books and the restrictions on parcels have been in existence across most of the prison estate for many years and for very good reason.”
She added: “We are considering how best to fulfil the ruling of the court. However, we are clear that we will not do anything that would create a new conduit for smuggling drugs and extremist materials into our prisons.”