BOOK REVIEW / NONFICTION : Vegetarianism’s History, Course by Course : THE HERETIC’S FEAST <i> by Colin Spencer</i> , University Press of New England, $29.95, 399 pages

About 25 years ago, Second City, the Chicago-based improvisational theater troupe, included in its repertoire a snide little sketch about vegetarians that contradicted the stereotype of the pale, passive carrot lover.

It was about two shoppers who encounter each other in a supermarket aisle--but each time the vegetarian was crossed he became more and more hostile, until he exploded in some kind of blood rage, as though he were, well, a carnivore.

Big laughs. Vegetarians have always gotten a bum rap for being somehow less than full-blooded; it is as though their refusal to eat flesh or its by-products (or wear it; I knew a kid in college who lived in fabric shoes and hemp belts) were a sign of timidity, an unwillingness to live life to its culinary fullness.

But the prolific writer Colin Spencer (novels, nonfiction, six plays produced, film and television scripts, and, of course, a dozen books on food) sets the record straight in this imposing history of vegetarianism.

Spencer quotes the playwright George Bernard Shaw, who insisted that his experience of life as a vegetarian was simply different from what the rest of the world went through:

“The odd thing about being a vegetarian,” Shaw said, “is not that the things that happen to other people don’t happen to me--they all do--but that they happen differently: Pain is different, pleasure different, fever different, cold different, even love different.” Spencer decided to examine the difference.

This is emphatically not a book for the devout foodie who wants to toss anecdotes around in between the cinghiale and the panna cotta; no sir.

Spencer traces contemporary issues that intersect with vegetarianism--objection to animal slaughter, concern for the environment, the quest for balance and health--back to 600 BC, and then marches through time up to the present day, showing us that vegetarians were often rebellious, active sorts.

For example: Does Wagner strike you as the shy retiring type? He managed simultaneously to hate Jews and consider animals the equal of humans, a nice bit of philosophical sashay, and believed that eating meat had corrupted the human race.

Hitler, who loved to listen to Wagner, absorbed his notions about diet and Jews--and Spencer puts Hitler’s vegetarianism into context as part of his rejection of the status quo. Spencer thinks that vegetarianism is part of a larger unwillingness to accept the way one’s society functions--a stepping-back, as a prelude to attempting a reorganization.

It is odd for a baby boomer to read about her own coming of age in such a distilled, academic fashion, the counterculture boiled down into a post-adolescent revolt that included a re-evaluation of all accepted tenets, including a suburban devotion to steak and fries, and the Swanson TV dinner.

But anyone who cares about what people eat--not the trendy dish of the month, but about diet and attitude, food and philosophy--will want to work through “The Heretic’s Feast.”

You just have to take it one course at a time, lest you feel a bit overstuffed and unable to go on.