The art of Robert Indiana is famed throughout the world. The problem is no one has heard of him.

Unlike some of his contemporaries in the Pop art movement — Andy Warhol, Roy Lichtenstein, and Jasper Johns, who have become household names — a mention of Mr. Indiana’s name in casual conversation is often mistaken as a geographic reference to the Midwestern state sandwiched between Illinois and Ohio. Although the artist has produced a significant volume of work over the last four decades, he has created only one image that is widely recognized: “LOVE.”

A tribute to his Christian upbringing as much as to the ethos of the 1960s flower-power generation, the artist’s iconic representation of that loaded four-letter word has been seared into the minds of people across the globe — in large part because it was immortalized on a 1973 American postage stamp and mailed to every country on Earth. But even more so since the artist translated his message into Spanish, Hebrew, and Chinese.

Framed in a square, the first two characters rest atop the others. Perhaps to remind us that love is imperfect, the letter “O” leans precariously to one side, as if it were about to tumble off of its perch. The design is simple yet so effective that the recognition it has received has dwarfed the reputation of its creator.

A new book, “Robert Indiana” (Rizzoli International, 304 pages, $75), aims to change that. Written by three highly regarded art experts — a professor emeritus at the City University of New York, Robert Pincus-Witten; a curator at New York’s Museum of Modern Art, Joachim Pissarro, and a Princeton professor of American art, John Wilmerding — the book’s stated goal is to show how the significance of the artist’s work has been underestimated. Mr. Indiana’s name, the authors contend, deserves to be added to the hagiography of Pop art icons.

Yet in their three short chapters, the authors fail to present the kind of evidence that would make a convincing case for that thesis.

For instance, where the reader might expect parallels to be drawn between Mr. Indiana and more celebrated names, Mr. Pissarro chooses instead to show what makes him different, arguing that Mr. Indiana openly embraced his “Yankee” roots while other Pop artists sought to distance themselves from the American tradition. He points out that Mr. Indiana has made use of American classics such as “Moby Dick” and “Leaves of Grass” as the inspirations for his hard-edged, brightly colored “signscapes” — which are meant to mimic garish advertisements — while the more-famous Lichtenstein argued that his own comic-strip-inspired work should not be seen as American but universal.

In Mr. Pincus-Witten’s essay, the curator throws down the heavy contention that Mr. Indiana is as much the source of Pop art’s obsession with letters and numbers as Jasper Johns. But without presenting a real case for this claim, the article then meanders on to briefly discuss the history of the Coenties slip artists — among whose group Mr. Indiana counted himself a member — before ending by restating the obvious: that the artist’s most well-known work has outshined the fruit of the rest of his career.

Mr. Wilmerding’s observations are perhaps the most useful in the book— he at least hints at some of the ways that Mr. Indiana’s art has reverberated throughout American culture. He cites a few of the most prominent examples, including several major advertising campaigns by companies such as Microsoft, Ralph Lauren, and the North Beach Leather Company, as well as the cover for the 2000 album “Renegades” by the rock group Rage Against the Machine, which recast the “LOVE” design as a tribute to a very different emotion: “RAGE.”

However, Mr. Wilmerding neglects to mention the Canadian art collective General Idea’s 1987 silkscreen poster, which heralded a new era in AIDS activism when it used the same famous motif for explicitly political purposes by replacing the spelling of love with the letters “A,” “I,” “D,” and “S.” The collective’s stated purpose was to remove the social stigma imposed on gay men who had developed the disease. Given Mr. Indiana’s own homosexuality as well as the strongly political nature of his art, this omission seems to be a rather major oversight for an essay attempting to demonstrate the cultural importance of the artist.

Still, Mr. Wilmerding’s nod to Indiana-inspired artifacts is the closest that the book comes to showing the Pop painter-sculptor’s true significance in American art (though not even one of the several examples mentioned is reproduced for the reader to see). The writer’s few brief paragraphs on the subject should have been expanded to encompass the entire book.

But luckily, the majority of the book’s 300-odd pages are filled with full-color reproductions of Mr. Indiana’s work, which demonstrate what the writers fail to articulate.

Readers can see for themselves that the bulk of Mr. Indiana’s oeuvre is imbued with vibrant contrasts that are as lively as anything by Warhol. Specifically, Mr. Indiana’s paintings and sculptures of the numbers zero through nine are done in sharp hues that give them a logo-like boldness that Jasper Johns’s more-famous number paintings lack. In contrast, Mr. Johns’s work seems understated and tentative.

Observers might also note that while Lichtenstein’s “Drowning Girl” yiped loquaciously — “I don’t care! I’d rather sink — than call Brad for help!” — Mr. Indiana manages to pack as much emotional drama and insight into his pointed use of just four one-syllable words: “EAT,” “HUG,” “ERR,” “DIE.”

Mr. Joseph is The New York Sun’s assistant editor for national and foreign news. He writes frequently about art and culture.