Like Richard Kluger's five previous books, this novel about a young man's coming of age during the Depression is notable for its gracious, witty prose, its wealth of research and its fervent political and moral convictions. It is obvious from "Un-American Activities" and everything else he has written--especially "Simple Justice," his history of the Brown desegregation decision--that Kluger is an eminently decent person whose instincts are unflaggingly generous and whose desire it is to promote, through his written works, the very best of causes.

Which is precisely the trouble with this interminable, exhausting novel. It is all well and good for a novelist to have his heart in the right place, but that is not worth a hill of beans if he fails to create a believable, interesting piece of fiction. This, in "Un-American Activities," is what Kluger has failed to do. He is so busy instructing us that he neglects to engage or entertain us; though a few characters and incidents sparkle, the novel as a whole is so long and so doggedly earnest that the mere act of paying attention soon enough becomes burdensome.

This is by striking contrast with Kluger's previous novel, "Star Witness," which in important respects is a quite similar piece of work. Its protagonist is also a young person learning the ways of a capricious, demanding world--she is a lawyer in her first job--and it, too, covers a broad range of political issues. But the lawyer, Tabor Hill, is a far more appealing character than Toby Ronan, the confused young man whose progress is the subject of "Un-American Activities"; and in "Star Witness," Kluger manages to tie his themes to a reasonably suspenseful plot--an ingredient completely missing, alas, in "Un-American Activities."

The story, which covers the full decade of the 1930s, begins with Ronan's matriculation at Harvard and ends with his much-delayed decision about what career to pursue. Really, though, it is three stories; the first is set in Cambridge, the second at a Civilian Conservation Corps camp in Western Massachusetts and the third in New York City. In all three, Ronan's idealism and naivete', his quest for "truth, justice and love," are tested by the struggles within a nation that, in a time of extreme hardship, is questioning the most fundamental beliefs on which it was founded.

Which is to say that from Harvard to New York, Ronan is challenged and tempted by the various forms of radicalism abroad in the land--challenges and temptations that come to him in the person of one alluring female after another. His mien may be wimpish, but he's catnip to the ladies, especially those who sing the siren songs of socialism and communism and all the other isms that appealed, in those days, to young people of good heart and impressionable mind. For nearly 700 pages, Ronan participates in sack sessions and bull sessions, at times simultaneously.

If dorm-room or coffeehouse dialectics are your cup of tea, then you'll find "Un-American Activities" a greater treat than a boatload of Orange Pekoe; not since Doris Lessing's "The Golden Notebook" has a novel been so relentlessly, unrelievedly crammed with political, philosophical chatter. Imagine yourself sentenced to a lifetime membership in the Dialectical and Philosophical Society, and you've got the picture. Or, to be more accurate, part of the picture; when Kluger isn't putting the debate squad through its paces, he's teaching civics lessons:

"America, he said, was great enough and strong enough to face the truth--namely, that it had undergone a great illness and still needed a good deal of rehabilitation--without having to tar every criticism or suggestion for achieving better health as an act of treason. 'It takes as much caring, as much patriotism, as much love, to say the flag is flying upside down and backwards as to stand there saluting it blindly.' "

All of which is absolutely true and unexceptionable, and please excuse me while I take a nap--which is just what I kept doing while struggling to turn the pages of "Un-American Activities." The novel does have its moments, in particular its depiction of Harvard in the early '30s and its portrayal of a couple of the women who for some reason are drawn to Toby Ronan. Too, Kluger's sincerity of purpose is manifestly attractive, and cannot be lightly dismissed. But it remains that, for all its author's good intentions, no spark of interest is lit by "Un-American Activities."