Each year on July 26, Fidel Castro celebrates the anniversary of the launching of his revolution in Cuba. This year the festivities can be seen in a different light. The price paid by Cuba's legions of political prisoners, who have made Castro the leading jailer in the world, is finally becoming clear.

The person most responsible for this change is Armando Valladares, whose memoir of his 22 years as Castro's prisoner came out here in May, following publication in Europe. ''Against All Hope'' is a book and a political event. For Valladares is the Cuban Solzhenitsyn, another writer whose report from a revolution's heart of darkness burst through the haze of propaganda, inattention and stale debate and brought the West's consciousness to a new place.

*As happens, ''Against All Hope'' has provoked reviews extending beyond the book into the political culture. Many ask how the phenomenon of innocents held in bestial prisons could have existed into the third decade of Cuban communism, yet only now does the general political community start to see it truly.

And only now does the mass of Cubans become concretely aware of the unjust incarceration and inhuman torture of their fellow citizens, thanks to the 10 programs based on the book broadcast to Cuba earlier this year by the American government's Radio Marti.

The American right, to account for the broader public's ignorance of Cuban prisons, pounces on what it sees as the propensity of American liberals to view Castro through rose-colored glasses -- for considerations of sympathy, ''peace,'' guilt, radical chic or whatever.

The left, which is embarrassed but perhaps not as much as it ought to be, cites circumstances. For instance, it is suggested apologetically that when the American human rights movement got up steam in the 1970s, its necessary priority was the immediate and gory outrages of right-wing regimes. Others suggest that the few releases of prisoners Castro has recently made, and the current possibility of negotiating the emigration of other Cuban prisoners, finally sensitized our public to the issue.

It is evident that Ronald Reagan has presided over changes in the political atmosphere that have finally made Castro's crimes both fair and necessary game -- and not only for Americans concerned with human rights but perhaps increasingly for Latins, whom Castro is otherwise so ready to instruct in anti-Yankee ways. But there is another consideration, one that goes to the peculiar relationship between politics and literature.

I had lunch with Armando Valladares in 1982 a few weeks after Castro released him in response to an appeal by French President Francois Mitterand. Valladares had written prison poems; the French are good about appealing for poets. Valladares was thin and gaunt, a man of sad eyes and halting speech, quiet and rather calm, strangely dispassionate: a victim of a terrible system, but -- how unfair it is to say this about him -- not a compelling figure or one with what seemed to me a compelling story. I recall thinking he was still sick and tired and in a strange place; translation added another veil.

Only his book made plain that here was one of the enduring works of prison literature, the century's distinguishing genre: a record of state violence and individual resistance, authentically told, inspiring, unforgettable. Television may be the medium of contemporary politics, but literature conveys the dimension of individual character. The one creates celebrities, the other heroes, like Armando Valladares.

Some in the West still regard Castro as the fun dictator, bask in the glow of six-hour talks with him, consider him someone we all need to understand better. Valladares seems to me to understand him perfectly, and closes his book with a lie Castro told in 1983, while Valladares was rotting: ''From our point of view, we have no human-rights problem -- there have been no 'disappeareds' here, there have been no tortures here, there have been no murders here. In 25 years of revolution, in spite of the difficulties and dangers we have passed through, torture has never been committed, a crime has never been committed.''