Four years after Justice John Paul Stevens retired from the Supreme Court in 2010, his wife, Maryan, threw a surprise party for his 94th birthday. The gathering of old friends summoned vivid memories of a long and eventful life, and it gave him an idea. He should write a memoir.

“I just started writing after that party,” Justice Stevens said by phone the other day from his home in Fort Lauderdale, Fla. “It kind of set me off.”

The book, “The Making of a Justice: My First 94 Years,” will be published in May, not long after Justice Stevens’s 99th birthday.

“It’s a long story,” Justice Stevens said.