Silverstein confirmed he never studied the poetry of others, and therefore developed his own style: laid-back and conversational, occasionally employing profanity, and slang.
He is most commonly known for writing and illustrating his children's literature including The Missing Piece, A Light In The Attic, Lafcadio(his first book), Where the Sidewalk Ends, Falling Up, The Giving Tree, A Giraffe and a Half, and The Missing Piece Meets the Big O. For adults he wrote Uncle Shelby's ABZ Book, a satirical mock children's book, and created Different Dances, a coffee table book of wordless, adult-themed cartoons. He continued to write colloquial poetry on occasion throughout his life, including a beatnik-hipster version of Shakespeare's Hamlet in Playboy magazine in 1998. He also co-wrote the screenplay Things Change with David Mamet.
In 2005, Runny Babbit: A Billy Sook, was published posthumously. As the title suggests, every poem and illustration in the book consists of spoonerisms. In an NPR interview, Mitch Myers, Shel Silverstein's nephew, who wrote the liner notes for a "Best of Shel Silverstein" CD and helped compile the new collection of poems, said, "I think he wasn't sure about how it would be received. It is and was very different. And it's not easy, even for adults to read. I think, actually, younger children have a better time at it because they're not so preconceived in their notions of how words work. And the playfulness of it really comes across." Silverstein said "I did not have any inspirations, my talent formed, because that was what I loved to do....(and forever will)", "Many kids should know their talents form in their heart and soul."
A blurb by Otto Penzler from his crime anthology Murder for Revenge (1998) states:
"The phrase "Renaissance man" tends to get overused these days, but apply it to Shel Silverstein and it practically begins to seem inadequate. Not only has he produced with seeming ease country music hits and popular songs, but he's been equally successful at turning his hand to poetry, short stories, plays, and children's books. Moreover, his whimsically hip fables, beloved by readers of all ages, have made him a stalwart of bestseller lists. A Light in the Attic, most remarkably, showed the kind of staying power on the New York Times chart—two years, to be precise—that most of the biggest names (John Grisham, Stephen King, and Michael Crichton) have never equaled for their own blockbusters.And there's still more: his unmistakable illustrative style is another crucial element to his appeal. Just as no writer sounds like Shel, no other artist's vision is as delightfully, sophisticatingly cockeyed.
One can only marvel that he makes the time to respond so kindly to his friends' requests. In the following work, let's be glad he did. Drawing on his characteristic passion for list making, he shows how the deed is not just in the wish but in the sublimation."
This anthology was the second in a series, which also included Murder for Love (1996) and Murder and Obsession (1999). All three anthologies included contributions by Shel Silverstein.
Most notably, he wrote the music and lyrics for "A Boy Named Sue" that was performed by Johnny Cash (for which Silverstein won a Grammy in 1970), "One's on the Way" (which was a hit for Loretta Lynn), and "The Unicorn", which, despite having nothing to do with Ireland nor Irish culture, became the signature piece for The Irish Rovers in 1968 and is popular in Irish pubs all over the world to this day. Another Silverstein song recorded by Cash is "25 Minutes to Go", sung from the point of view of a man facing his last 25 minutes on Death Row, with each line of the song counting down one minute closer. He wrote the lyrics and music for most of the Dr. Hook & The Medicine Show songs, including "The Cover of the Rolling Stone", "Freakin' at the Freakers' Ball", "Sylvia's Mother", and the cautionary song about venereal disease, "Don't Give a Dose To the One You Love Most". He also wrote many of the songs performed by Bobby Bare, including "Rosalie's Good Eats Cafe", "The Mermaid", "The Winner", "Tequila Sheila," and a co-write with Baxter Taylor for the song "Marie Laveau" for which the songwriters received a BMI Award in 1975. "The Mermaid" was also covered in 2005 by Great Big Sea, who released their version on their CD The Hard and the Easy. The song "The Ballad of Lucy Jordan", recorded in 1979 by Marianne Faithfull and later featured in the films Montenegro and Thelma & Louise, was also by Silverstein, as was "Queen of the Silver Dollar", which appeared on Emmylou Harris' 1975 album Pieces of the Sky and was also covered by "Dave & Sugar". He was nominated for an Oscar for his music for the film Postcards from the Edge. He also composed original music for several other films, and displayed a musical versatility in these projects, playing guitar, piano, saxophone, and trombone.
Silverstein's songs, performed by Waylon Jennings and Kris Kristofferson among others, comprise the soundtrack to the 1970 film Ned Kelly.
Silverstein also had a popular following on Dr. Demento's radio show. Among his best-known comedy songs were "Sarah Cynthia Sylvia Stout (Would Not Take The Garbage Out)", "The Smoke Off" (a tale of a contest to determine who could roll—or smoke—marijuana joints faster), and "I Got Stoned and I Missed It". He also wrote "The Father of a Boy Named Sue", in which he tells the story from the original song from the father's point of view, and the 1962 song "Boa Constrictor" that is sung by a man who is being progressively swallowed whole by a snake (recorded by the folk group The Brothers Four), although it is now better known as a children's playground chant.
A longtime friend of American singer and songwriter Pat Dailey, Silverstein collaborated with Dailey on the (posthumously released) 2002 Underwater Land album. It contains 17 children's songs written and produced by Silverstein and sung by Dailey. Silverstein also appears along with Dailey on a few tracks. The album also contains artwork by Silverstein.
Silverstein was posthumously inducted into the Nashville Songwriters Hall of Fame in 2002.
An Adult Evening of Shel Silverstein was produced by the Atlantic Theater Company in New York City in September 2001. The collection of short sketches, directed by Karen Kohlhaas, comprised the following:
Shel's Shorts was produced in repertory as two separate evenings under the titles Signs of Trouble and Shel Shocked by the Market Theater in Cambridge, Massachusetts in December 2001. Signs of Trouble was directed by Wesley Savick, and Shel Shocked was directed by Larry Coen.
The Mind of Shel Silverstein was a collection of Shel Silverstein poems from "Where the Sidewalk Ends," "A Light in the Attic," and "Falling Up," that was directed for the stage in 2007 by Jesse S. Martinez for Marana Middle School's Off Freeway Performers in Marana, Arizona.
Silverstein's other child was his son Matthew, born on November 10, 1983. Silverstein's 1996 Falling Up was dedicated to Matt. Matthew's mother is alleged to be the "Sarah" mentioned in the other thanks for Falling Up.
Shel Silverstein died sometime during the weekend of May 8, 1999, in Key West, Florida, of a heart attack. His body was found by two housekeepers the following Monday, May 10. It was reported that he could have died on either day that weekend (Saturday or Sunday).
"When I was a kid—12, 14, around there—I would much rather have been a good baseball player or a hit with the girls. But I couldn't play ball, I couldn't dance. Luckily, the girls didn't want me; not much I could do about that. So, I started to draw and to write. I was also lucky that I didn't have anybody to copy, be impressed by. I had developed my own style, I was creating before I knew there was a Thurber, a Benchley, a Price and a Steinberg. I never saw their work till I was around 30. By the time I got to where I was attracting girls, I was already into work, and it was more important to me. Not that I wouldn't rather make love, but the work has become a habit."
--(Jean F. Mercier. "Shel Silverstein", Publishers Weekly, February 24, 1975).
Silverstein did not really care to conform to any sort of norm, but he did want to leave his mark for others to be inspired by:
"I would hope that people, no matter what age, would find something to identify with in my books, pick up one and experience a personal sense of discovery. That's great. But for them, not for me. I think that if you're creative person, you should just go about your business, do your work and not care about how it's received. I never read reviews because if you believe the good ones you have to believe the bad ones too. Not that I don't care about success. I do, but only because it lets me do what I want. I was always prepared for success but that means that I have to be prepared for failure too.--Shel Silverstein, from Publishers Weekly, February 24, 1975I have an ego, I have ideas, I want to be articulate, to communicate but in my own way. People who say they create only for themselves and don't care if they are published...I hate to hear talk like that. If it's good, it's too good not to share. That's the way I feel about my work. So I'll keep on communicating, but only my way. Lots of things I won't do. I won't go on television because who am I talking to? Johnny Carson? The camera? Twenty million people I can't see? Uh-uh. And I won't give any more interviews."
The few interviews he did give throughout his life gave insight to his thinking patterns. One example of these interviews:
Question: "Why do you have a beard?" Shel: "I don't have a beard. It's just the light; it plays funny tricks." Question: "How do you think your present image as world traveler, bawdy singer, etc. combines with your image as a writer of children's books?" Shel: "I don't think about my image." Question: "Do you admit that your songs and drawings have a certain amount of vulgarity in them?" Shel: "No, but I hope they have a certain amount of realism in them." Question: "Do you shave your head for effect or to be different, or to strike back at the long-haired styles of today? Shel: "I don't explain my head."--(1965) from the album I'm So Good That I Don't Have to Brag.
Silverstein believed that written works needed to be read on paper – the correct paper for the particular work. He usually would not allow his poems or stories to be published unless he could choose the type, size, shape, color, and quality of the paper himself. Being a book collector, he took seriously the feel of the paper, the look of the book from the inside and out, the typeface for each poem, and the binding of his books. He did not allow his books to be published in paperback as he did not want his work to diminish in any way.
Shel Silverstein also recorded numerous unreleased songs. Some were found at A&R Recording Studio in New York, but never officially released—though bootleg albums of these exist. These songs are generally more vulgar than his other material. Most are thought to have been recorded around 1969-1970, although they resemble the Songs & Stories musical and lyrical style of 1978.Shel also sang poems.