Among his volumes of comic book and comic strip history are The Adventurous Decade: Comic Strips in the 1930s (1975) and Comic Book Encyclopedia (2004). Cheap Thrills: An Informal History of the Pulp Magazines (1972) is his best known non-fiction book, and The Hardboiled Dicks: An Anthology and Study of Pulp Detective Fiction (1967) has also been influential. He contributed to P.S. and other magazines, along with his book review column for Venture Science Fiction Magazine.

Goulart's fiction is characterized by several themes, notably humor, technology gone wrong (usually through incompetence rather than malice) and heroes with superhuman powers. His humorous crime and science fiction includes tales about robots and historical Hollywood figures, such as Groucho Marx. In the 1970s, he wrote several Phantom novels featuring Lee Falk's The Phantom for Avon Books, using the pseudonym "Frank Shawn" (a play on his wife and son's names), and he has also written Phantom comic book stories and short stories for Moonstone Books from 2003 and beyond.

It is widely known that Goulart ghost wrote the popular TekWar series of books credited to the actor William Shatner (Shatner is said to have written the outlines for the books). He has also ghosted novels featuring the Phantom, Flash Gordon and the pulp character the Avenger. In addition, he has written scripts for a number of comics, including the Star Hawks comic strip he created with artist Gil Kane, as well as the comic book version of TekWar.

A collection of his mystery short stories, Adam and Eve on a Raft, was published in 2001 by Crippen & Landru.

Goulart is married to author Frances Sheridan Goulart and has two sons, Sean-Lucien and Steffan Eamon.