In his preface, Bryan Caplan writes:
Yet almost no one questioned the socialists' idealism. By 1961, however, the descendents of the radical wing of the Social Democratic Party had built the Berlin Wall — and were shooting anyone who tried to flee their "Workers' Paradise."…Who could have foreseen such a mythic transformation?
Eugene Richter, that's who, in 1893. There is now a reissue of Richter's Pictures of the Socialistic Future. There is an interview with Bryan Caplan about the book here. Here is the book on-line and free.