Gilbert, who was attended by a group of friends when he passed at a nursing home in Berkeley, Calif., gained international acclaim with his 1962 collection of poems "Views of Jeopardy," which won the Yale Younger Poets Prize and was nominated for the Pulitzer Prize, the Los Angeles Times noted.
"I think it's fair to say that Jack was America's greatest living poet," Mayer told the Times in a telephone interview. "He was unique in that he was not a part of any [literary] school or group. He went his own way, and he lived pretty much entirely for his life and his art."
The newspaper categorized Gilbert as a literary rebel among rebels known as an intimidating personality who made many enemies among the literary establishment.
"I want poems that matter," the Times quoted him as having said.
After "Views of Jeopardy" was published, Gilbert walked away from the public attention, traveling abroad before returning to the United States to teach at San Francisco State and start a poetry workshop.
He seldom published any works until "Monolithos" in 1982, which was a Pulitzer finalist. Three more collections, and more awards, followed, though his works haven't found their way into modern anthologies.
The Times noted some critics disliked his repeated use of familiar themes such as the moon, the Aegean and women's breasts. But his admirers point to the emotion he brought to bear while writing in a spare and direct style.
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