Symons was the eldest of four sons and a daughter born to auctioneer Morris (or Maurice) Albert Symons (died 1929), of Russian-Polish Jewish immigrant parentage, and Minnie Louise (died 1964), née Bull.
He was obliged to enter a trade at the age of fourteen,[4] and for three years led a "life of drudgery" apprenticed to a furrier.
In 1924 he published a bibliography of first editions of the works of Yeats, and in 1930 he founded the Book Collector's Quarterly.
Subtitled "An experiment in biography," The Quest for Corvo was a groundbreaking work: rather than being a simple narrative of a life, it describes an author's search for understanding of his subject, revealing aspects of Rolfe's life and character as they are revealed to the author.
He left several unfinished works, including a long-contemplated biography of Oscar Wilde, at his death.