Folk singer and activist Pete Seeger turned 90 on May 3, and at least two new biographies are stepping onto the stage to mark the occasion. First up at the microphone is Alec Wilkinson, author of “The Protest Singer: An Intimate Portrait of Pete Seeger.” Wilkinson’s brief book is expertly constructed, fitting a retrospective of Seeger’s complicated life onto a long interview that Wilkinson conducted with him at Seeger’s home in upstate New York. It reads smoothly and easily.

The content, however, is disappointingly simplistic. “The Protest Singer” is unabashedly admiring and therefore completely one-sided; there is no attempt to critique seriously Seeger’s political ideas, which included a short stint in the Communist Party.

Anyone who disagrees with Seeger is presented as a bully, a buffoon or a selfish prig. If you buy Wilkinson’s argument, Seeger has never had a jealous or unkind thought, never played a single chord or written a single sentence for anything as grubby and shallow as money. “He dislikes being so well known,” Wilkinson writes. That, of course, is the familiar lament of the famous: I hate being a celebrity!”

Seeger’s talent is undeniable, and his music is an essential part of American culture. He has done many wonderful things for the world. But a more balanced portrait — nobody is all good, all the time — would have made Seeger seem even more remarkable. It’s the demons that are confronted and defeated — not the alleged lack of demons — that makes the true hero.

To be sure, Wilkinson’s writing is sharp and clear: “When I arrived Seeger was sitting on the grass and feeding logs into the fire. It was a cold, raw day. … He was wearing jeans and a cloth coat and a knitted wool hat with a pom-pom on it.” If only the author, a New Yorker staff writer, had brought that same sharpness and clarity to a more balanced, less starry-eyed enterprise.