His father, Sir Stevenson Arthur Blackwood, was a Post Office administrator; his mother, Harriet Dobbs, was the widow of the 6th Duke of Manchester.

[5] After Algernon read the work of a Hindu sage left behind at his parents' house, he developed an interest in Buddhism and other eastern philosophies.

Like his lonely but fundamentally optimistic protagonists, he was a combination of mystic and outdoorsman; when he wasn't steeping himself in occultism, including Rosicrucianism, or Buddhism he was likely to be skiing or mountain climbing.

Good examples are the novels The Centaur, which reaches a climax with a traveller's sight of a herd of the mythical creatures; and Julius LeVallon and its sequel The Bright Messenger, which deal with reincarnation and the possibility of a new, mystical evolution of human consciousness.

In correspondence with Peter Penzoldt, Blackwood wrote,[13] My fundamental interest, I suppose, is signs and proofs of other powers that lie hidden in us all; the extension, in other words, of human faculty.

Blackwood wrote an autobiography of his early years, Episodes Before Thirty (1923), and there is a biography, Starlight Man, by Mike Ashley (ISBN 0-7867-0928-6).

In The Books in My Life, Henry Miller chose Blackwood's The Bright Messenger as "the most extraordinary novel on psychoanalysis, one that dwarfs the subject.

"[14] Authors who have been influenced by Blackwood's work include William Hope Hodgson,[15] George Allan England,[16] H. Russell Wakefield,[17] "L. Adams Beck" (Elizabeth Louisa Moresby),[18] Margery Lawrence,[19] Evangeline Walton,[20] Ramsey Campbell[21] and Graham Joyce.

[22] In the first draft of his guidance notes to translators of his work, "Nomenclature of The Lord of the Rings", J. R. R. Tolkien stated that he derived the phrase "crack of doom" from an unnamed story by Blackwood.

[23] In her book, Tolkien's Modern Reading, Holly Ordway states that this unnamed Blackwood work is his 1909 novel The Education of Uncle Paul.

[33] Christopher Matthew Scott analyzes Blackwood's use of Christian symbolism and story setting as connected to the author's biography; describing a spiritual progression up from hellish city, through garden, forest, and mountain.