Macdonald was born in 1954, and raised in White Plains, New York. He attended the University of Rochester, and went on to serve in the US Navy for fifteen years. He has been writing professionally since the early 1990s and has published 35 novels.

Macdonald is well known for his work in educating aspiring authors, particularly for his advice on avoiding literary scams. Early in his career he was asked by such an author how much he had paid to have his books published, and in response began a campaign of educating other writers about the problems of vanity publishers. As part of this campaign, he coined Yog's Law, which states "Money should flow toward the author," which is often quoted by professional authors when giving advice on getting published (such as John Scalzi, Teresa Nielsen Hayden).

Atlanta Nights and PublishAmerica

One target of his campaign is PublishAmerica, a company that claims not to be a vanity publisher but a "traditional publisher" that accepts or rejects books based on their quality. Macdonald organized a group of professional authors to test whether that company was actually reading any submissions for clarity and realism before accepting them. One day after Macdonald issued a press release announcing that PublishAmerica had accepted a manuscript that was created to be as bad as possible, the company withdrew the offer to publish it.

Knight's Wyrd was awarded the Mythopoeic Fantasy Award for Children's literature, 1992, and named to the New York Public Library Books for the Teen Age list in 1993. In 1997, he was awarded Best Young-Adult Science Fiction by the Science Fiction Chronicle for Groogleman.

Novels

• The Apocalypse Door, Tor (New York, NY), 2002.

Novels with Debra Doyle

• (Under pseudonym Robyn Tallis) Night of Ghosts and Lightning ("Planet Builders" series), Ivy, 1989.
• (Under pseudonym Robyn Tallis) Zero-Sum Games ("Planet Builders" series), Ivy, 1989.
• (Under pseudonym Victor Appleton) Monster Machine ("Tom Swift" series), Pocket Books (New York, NY), 1991.
• (Under pseudonym Victor Appleton) Aquatech Warriors ("Tom Swift" series), Pocket Books (New York, NY), 1991.
• Timecrime, Inc. ("Robert Silverberg's 'Time Tours'" series), Harper (New York, NY), 1991.
• Night of the Living Rat ("Daniel Pinkwater's 'Melvinge of the Megaverse'" series), Ace Books (New York, NY), 1992.
• Knight's Wyrd, Harcourt, Brace (New York, NY), 1992.
• Groogleman, Harcourt, Brace (New York, NY), 1996.
• Requiem for Boone (based on the television series Gene Roddenberry's Earth...Final Conflict), Tor (New York, NY), 2000.
• (As Douglas Morgan) Tiger Cruise, Forge (New York, NY), 2001.
• (As Douglas Morgan) What Do You with a Drunken Sailor? (nonfiction), Swordsmith, 2002.
• Land of Mist and Snow, Eos, 2006

"Circle of Magic/The Wizard Apprentice" series, with Debra Doyle

• School of Wizardry, Troll (Metuchen, NJ), 1990.
• Tournament and Tower/The Secret of the Tower, Troll (Metuchen, NJ), 1990.
• City by the Sea/The Wizard's Statue, Troll (Metuchen, NJ), 1990.
• The Prince's Players/Danger in the Palace, Troll (Metuchen, NJ), 1990.
• The Prisoners of Bell Castle/The Wizard's Castle, Troll (Metuchen, NJ), 1990.
• The High King's Daughter, Troll (Metuchen, NJ), 1990.
• Mystery at the Wizardry School, Troll (Metuchen NJ), 2003. [This book was not written by the authors James D. Macdonald and Debra Doyle, they only wrote the first 6]
• Voice of the Ice,Cloverdale Press, 2003.

Horror High series

All written with Debra Doyle under the joint pseudonym "Nicholas Adams."

1. Horror High: Mister Popularity
2. Horror High: Resolved: You're Dead
3. Horror High: Heartbreaker
4. Horror High: New Kid on the Block
5. Horror High: Hard Rock
6. Horror High: Sudden Death
7. Horror High: Pep Rally
8. Horror High: Final Curtain
9. Horror High: Blood Game
10. Horror High: Deadly Secret
11. Horror High: Voice of Evil
12. Horror High: You're Dead

"Mageworld" series, with Debra Doyle

• The Price of the Stars, Tor Books (New York, NY), 1992.
• Starpilot's Grave, Tor (New York, NY), 1993.
• By Honor Betray'd, Tor (New York, NY), 1994.
• The Gathering Flame, Tor (New York, NY), 1995.
• The Long Hunt, Tor (New York, NY) 1996.
• The Stars Asunder, Tor (New York, NY) 1999.
• A Working of Stars, Tor (New York, NY), 2002.

"Bad Blood" series, with Debra Doyle

• Bad Blood, Berkley (New York, NY), 1993.
• Hunters' Moon, Berkley (New York, NY), 1994.
• Judgment Night, Berkley (New York, NY), 1995.

Under joint pseudonym "Martin Delrio," with Debra Doyle

• Mortal Kombat (movie novelization), Tor (New York, NY), 1995.
• Midnight Justice ("Spider-Man Super-Thriller" series), Byron Preiss (New York, NY), 1996.
• Global War ("Spider-Man Super-Thriller" series), Byron Preiss (New York, NY), 1996.
• Harold R. Foster's Prince Valiant (movie novelization), Avon (New York, NY), 1998.
• The Loch Ness Monster (nonfiction), Rosen Publishing (New York, NY), 2002.
• Truth and Shadows (novel; "MechWarrior: Dark Age" series), Roc (New York, NY), 2003.