Space was not the final frontier for William Shatner and Leonard Nimoy, friendship was. The two actors, who became part of pop culture as Capt. Kirk and Mr. Spock on TV’s “Star Trek,” forged a bond that lasted from the late ’60s to Nimoy’s death last year.

Now Shatner recounts stories of their professional and personal relationships in his book “Leonard” (Thomas Dunne Books, $25.99), which comes out Feb. 16. Though the two were “respectful, polite and professional” to one another when the series began, they eventually became close friends who shared many happy moments and also supported each other at darker times. Here are some of the most illuminating moments Shatner reveals about the man who wanted to be known as more than just Mr. Spock.

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WHAT’S THE POINT OF SPOCK’S EARS? Early promotion for “Star Trek” featured touched-up photos in which Mr. Spock’s pointed ears had been smoothed down. NBC was concerned that the “Dumbo” ears, as Nimoy referred to them, looked too devilish and would make the show a hard sell in the nation’s Bible Belt.

BATTLING THE BOTTLE Nimoy started drinking heavily during the second season of “Star Trek,” eventually turning to Alcoholics Anonymous and achieving sobriety after marrying his second wife, actress Susan Bay, in 1989. He offered his support to Shatner, whose third wife, Nerine Kidd, was also an alcoholic and died in 1999 after drowning in the couple’s pool.

A FATHER-SON FACEOFF The relationship between Nimoy and his son, Adam, was strained, to say the least. The career-driven Nimoy was often absent when his son was growing up, a situation exacerbated by Nimoy’s alcoholism. By 2006, they barely spoke to one another, but finally reconciled a few years before Nimoy’s death.

YOU CALL THAT MUSIC? Both Shatner and Nimoy had, what the author calls “successful — though critically questionable — musical careers.” Each made several albums, with several tracks (Nimoy’s rendition of “Proud Mary,” Shatner’s “Mr. Tambourine Man”) landing on the “Golden Throats” albums of musical oddities.

A TRUE ARTIST Nimoy was a man of many passions, including flying (he was a licensed pilot), photography and live theater. He also wrote and starred in a one-man show called “Vincent,” based on the letters between Vincent van Gogh and his brother, Theo. And no, he did not have van Gogh cut off a pointed ear.