In the spring of 1965, Ronald Reagan slipped into a ritzy Los Angeles restaurant. He was there to meet Stu Spencer, a political consultant he hoped would join his potential campaign for governor.

The year before, Reagan had famously stumped for the GOP’s presidential nominee, Barry Goldwater, who proved way too extreme for American voters. Spencer was worried the same was true of Reagan, but he found him to be flexible and smart. In fact, he found him to be downright literary. “I wrote a book,” Reagan told Spencer near the end of their meeting. “How’s that going to fit?”

Rather nicely, it turned out. Although it’s been forgotten today, in its own time “Where’s the Rest of Me?” was a big seller and a key artifact of California politics. The book also proves that Reagan was never just an actor, reciting the lines of Spencer-style political pros. Even in the early 1960s, Reagan was defining his image and defending his philosophy all by himself.

Reagan has never received enough credit for his intellectual side. As a child, he devoured books, and he was so taken by King Arthur tales he named his cat Sir Lancelot. As an actor, he spent his on-set breaks reading, often boring his co-stars with current affairs facts. Reagan eventually was elected president of the Screen Actors Guild more than once, before moving to TV and “General Electric Theater.” At GE factories he gave speeches based on books by economists whose views transformed him from an FDR-style Democrat to a conservative. He began to consider running for something bigger than the SAG presidency.

While Reagan’s biographers have explored the influence of GE and SAG on the budding politician, they’ve largely ignored what came next — namely “Where’s the Rest of Me?” In 1962, a New York publisher had asked Reagan if he wanted to write “a dramatic firsthand narrative,” as the editor put it, about his SAG battles against “the communist cancer in Hollywood.”

The idea must have appealed to a reader like Reagan. He surely saw its political potential. John F. Kennedy’s “Profiles in Courage” and Goldwater’s “Conscience of a Conservative” had proved that campaign books could stir interest and shape images. Once he started writing, in early 1963, Reagan changed the angle from a Hollywood story to a full autobiography that could address his biggest weaknesses as a candidate for governor: the charge that he was a mere actor and that he was a far-right extremist.

Reagan got help from Richard Hubler, a talented ghostwriter. They shared a sense of humor, with Hubler calling their project “the saga of Reagan” while Reagan called it “my literary epic.” They also shared a work ethic. They met at Reagan’s Pacific Palisades home in Los Angeles, outfitted with GE gadgets (electric iron, electric waffle maker). The ghost rarely needed to prompt his partner, who dug deep into such difficult topics as his father’s alcoholism and union battles.

“Where’s the Rest of Me?” is a surprisingly good read among presidential books, a revealing look at Reagan’s pre-political life that lacks the cautious muffling of political handlers.

Consider its opening: “The story begins with the close-up of a bottom in a small town called Tampico in Illinois, on February 6, 1911. My face was blue from screaming, my bottom was red from whacking, and my father claimed afterward that he was white.” The punch line was pure Reagan: “Ever since,” he wrote, “I have been particularly fond of the colors that were exhibited — red, white, and blue.”

“Where’s the Rest of Me?” portrays Reagan’s biography as serious and his politics as mainstream. The best example comes in the book’s final pages, which, according to a cache of letters no previous biographer has seen, went through at least two major revisions. Reagan argued that his objections to big government were considered “a nonpartisan viewpoint” in the Eisenhower era. Only after a Democrat took the White House did his perspective morph into so-called right-wing extremism. He also made the safest play in politics, adding a paragraph that invoked Lincoln.

Reagan’s ideas were debatable, of course, but the fascinating thing is that his image-shaping book predates handlers like Spencer and the wealthy team of “friends” who backed him for California governor and later president. When the book appeared, in 1965, it sold 200,000 copies and won national praise. As one reviewer put it, the book “may make Ronald Reagan governor.”

At this point, Spencer and a wealthy team of Reagan-boosting “friends” stepped in. They wanted to test Reagan as a retail politician, and his book signings provided the perfect cover. At one LA bookstore, Reagan arrived straight from his horse ranch. “He showed up in his English riding gear, breeches, boots, everything but the whip,” Spencer remembered. Even in that getup, Reagan charmed the crowd. At another signing, in Long Beach, a reporter asked for an answer to the question posed by the title: I found the rest of me, Reagan replied, “in politics.”

Reagan’s chief opponents for governor — George Christopher in the primary, incumbent Gov. Pat Brown in the general — viewed “Where’s the Rest of Me?” as a corny weak spot. Lou Cannon, who covered the race as a reporter, was offered the book by a Reagan staffer. “I already got my copy from your opponents,” Cannon replied, and they both had a good laugh.

Yet the attacks were less sophisticated than the book. Christopher carried an underlined copy to interviews so he could prove something Reagan never hid: He had once been a Democrat. “Where’s the rest of me?” Brown would ask on the stump, reminding the voters of the well-regarded book as much as its author’s conservative views. For his part, Reagan ignored the gibes, playing the part of the disciplined moderate. He won easily, and his book could only have helped.

The book also revealed something about Reagan’s independence and instincts. Early in the campaign, he’d given Spencer the political pro a copy. “To Stu,” he wrote inside it, “Who probably has an idea about what the rest of me should look like.” But Reagan already knew what he needed to look like. The proof was right there in the book he’d inscribed.

Craig Fehrman is the author of the new book “Author in Chief: The Untold Story of Our Presidents and the Books They Wrote,” from which this essay is adapted.