During the past decade, the Soviet Union's most gifted writer has become an un-person within his own country. Medvedev, a well-known Russian biologist, liberal, and friend of Solzhenitsyn, plots the course of the repression of creative writers and artists since Khrushchev's ouster in 1964. The rightward turn had begun the year before when Solzhenitsyn was denied the Lenin Prize. GAVLIT, the constitutionally illegal but very real organization that censors art and literature (""composed of less successful employees of publishing houses,"" says Medvedev), increasingly refused to pass the works of Solzhenitsyn and others. By 1966 there was no further mention of Ivan Denisovich; the secret police confiscated The First Circle; Sinyavsky and Daniel were arrested; in 1969 Solzhenitsyn was clumsily thrown out of the Writers' Union, and the regime wrecked the journal Novy Mir by deposing editor Tvardovsky. The 1970 Nobel award to Solzhenitsyn sent the official propaganda apparatus into paroxysms of slander and persecution of the literati. Now Medvedev fears -- apparently with good reason -- ""we are approaching another reign of violence and terror."" Few readers would question the authenticity of the book's account, and its conclusion is a convincing one.