Having for years faithfully followed all the fantastic feats of the famous black stallion and his owner-rider, Alec Ramsey, we find it difficult to believe that Alec would be careless enough to let his $100,000 horse-barn burn to the ground the very night he discovers his insurance on said barn has lapsed. Be that as it may, Mr. Farley uses it [in "The Black Stallion's Courage"] as an excuse (as if he needed one) to let the Black run again to glory….
Marjorie Burger, "The Black Runs Again: 'The Black Stallion's Courage'," in The New York Times Book Review (© 1956 by The New York Times Company; reprinted by permission), November 11, 1956, p. 42.
One must grant recognition to the almost fanatical devotion of the Walter Farley fans, and the Black himself has won his own coterie. But [The Black Stallion Mystery] is—for this reader anyhow—a disappointment. The story rarely achieves more than a rambling gait as horse and owner fly to Spain in search of the Black's famous Arabian sire. They locate him, not too convincingly, in a mysterious unnamed European country where his owner, Sheikh Abd-al-Rahman, raises horses on a mountaintop, complete with hanging gardens, Victorian coaches and liveried coachmen. The Sheikh's wife tries to kill the Black to avenge the death of her father, who had died in a fall from the Black long years before…. If this were not Walter Farley, one would be inclined to say "N-E-I-G-H" to this.
"Fiction: 'The Black Stallion Mystery'," in Virginia Kirkus' Service, Vol. XXV, No. 14, July 15, 1957, p. 487.