Sid Caesar; native American rights; and more; Hitler's least-known camp; Escape from Sobibor, by Richard Rashke. Boston: Houghton Mifflin Company. 389 pp. $15.95.

Sobibor was one of Hitler's most diabolical extermination camps, where 250, 000 Jews took their final walk to the ''showers.'' It also became the scene of World War II's largest prisoner escape, when hundreds revolted against their guards, broke through the walls, and bolted for the surrounding forest.

Today, almost 40 years later, neither the camp nor the escape are widely known - yet both deserve to be remembered.

Journalist Richard Rashke bases his account on the eyewitness recollections of 18 Sobibor survivors, buttressed with careful historical research. He recounts how 15-year-old Shlomo stays alive by fashioning rings for Nazis from the gold fillings of their victims; how Selma and Chaim, a Dutch girl and a Pole , fall in love in the midst of horror; how Sasha, a captured Red Army soldier, helps hatch the plot that brings them to freedom.

Rashke's narrative is vivid and dramatic. The events at Sobibor are unspeakable; the animosity the survivors encounter after their escape is an unexpected nightmare.

In the course of his research, Rashke found that the Sobibor ordeal left some survivors cynical; others, although haunted, retained their faith. But all share one quality: They dared to hope where there was no hope - if only to live another day.