Sidney Lens--Trotskyite, union militant, midwest peacenik--is that rarity, an American with a radical world view and a lifetime of second-rank service to leftist causes. Who else would speak, even jocularly, of a childhood wasted because he wasn't aware, at five, of the Russian Revolution? For Lens, caught up at 18 in the Depression, the decision not to join the Communist Party (in part because of ""an intense desire to become a writer,"" an occupation ""for rebels and introverts"") was, ipso facto, a decision to join the Trotskyites--an allegiance to which he gave over his life till the end of the Forties, living in furnished rooms, working in restaurants, seeing almost no one but party members, and organizing, pamphleting, protesting. He decries the factionalism that decimated the movement, lauds the abilities of his cohorts (most of whom, he says, gained prominent positions), and speaks of the excitement of feeling, in that ""red decade,"" that ""we were on the side of history."" (""The smallest group,"" they thought, ""could grow like wildfire""--or like the Bolsheviks--at the propitious moment if it had the ""correct line."") Lens made his own contribution in organizing Chicago retail workers--he remained a union official into the 1960s--and, moreover, tackling tough situations; he knows all about Communist and employer stratagems. And he'll tell you how business learned to live with unionization--by offering security (the closed shop, long-term contracts) to labor officialdom. But post-World War II, he writes, it was obvious that ""we leftists"" were wrong in ""our expectations"" (though not ""in our evaluation of capitalism"") and that the only feasible course was single-issue politics. Lens hooked up again with radical pacifist A. J. Muste, started to write seriously, traveled the world as a ""third camp socialist,"" took heart from Castro's coming in Cuba, and linked up at the outset with the peace movement--whose course is described in politically-astute, always interesting detail. Today he believes that the much-awaited revolution may come in stages, and better so--""because there is a minimum of bloodshed and political power remains dispersed."" But one doesn't read Lens so much for specific ideas as for the prevalence of ideas--and the testimony of experience.