You did 650 interviews for your Beatles book, which took you six years to write. You once said it even cost you your marriage. Was it an all-consuming thing for you to write the book? 

The Beatles book actually took eight and a half years to write. The book didn’t cost me a marriage; it was a lying ex-wife. But that aside, it was an all-consuming project. My office was submerged in over 50,000 pages of research, and a manuscript that eventually weighed in at 2,800 pages. I sat on a swivel chair and had notebooks open in a circle on the floor around me. I felt like Nigel Olson playing the drums for Elton John. Crazily, we cut 1,700 pages in the final edit, and a lot of fabulous stories wound up in the bin. But what I realized while working on the manuscript, was that I was writing the story of my life. I was in my early teens when the Beatles surged onto the scene, and they changed everything about being a teenager ever after — our look, our desires, our politics, our music, the works. So the book took on a monumental feel. The Beatles’ story was a miracle in itself — four friends from the streets of Liverpool who have a dream and change the world. And for eight and a half years I got to listen — intently — to one of the greatest catalogues of music. And I met a cast of incredible folks whose stories were so incredibly captivating and put the Beatles’ story in sharp perspective. Lastly, it dawned on me that I was actually the Beatles’ biographer — what a gorgeous gift to me.

When I read the book I came away with awe for Paul for his late-period Beatles work. Is it safe to say Paul was at his creative zenith in that 1966-69 period, and was it because he knew things were coming to an end?

I think Paul was at his creative zenith for much of the ten years the band was together. Remember, this was a 22-year-old who woke up one morning with “Yesterday” completely fleshed out in his head. He was the guy who laid out most of “Can’t Buy Me Love,” “Got to Get You Into My Head,” and “Eleanor Rigby” mid-career. And let’s face it, he basically invented the rock bass, launching it as a definitive rock ’n roll instrument and developing it in a way similar to what Jimi Hendrix and Jeff Beck did to the guitar. The stuff just poured out of Paul, the same way it did for Dylan while he was in his early 20s.

Did you watch Get Back? Did you learn anything in the footage that you didn’t know before?

I had seen some of the footage that was in Get Back while I was researching the biography, but it wasn’t until I sat through all eight hours of the Peter Jackson documentary that I wanted to go back and rewrite the end of my book. It didn’t change my mind, per se, but it added details that were unattainable to me when I was researching the biography. In any case, I sat through the entire three segments of the doc with a loopy grin on my face. It was such a pleasure for me to reunite with them again and to watch how they interacted with each other, a furtherance of the remarkable interaction that gave us their music. Especially between John and Paul. They could look at each other and know what the other was thinking. Uncanny! One thing I’ve always been adamant about, and was born out in the documentary, was their deep-down friendship, unbreakable even as the band was coming apart. They were mates first and foremost, and it’s so apparent in the documentary.

You recently wrote a Led Zeppelin book, which you wrote as not originally a Zep super fan. Are you a super fan now?

I really enjoyed working on the Led Zeppelin biography. I even think it’s my best book. Am I a super-fan? No. I’ve grown to enjoy their music, but one thing has always held me back from going whole-hog, so to speak, and that is Jimmy Page’s inability to write songs. Jimmy wrote riffs that he crocheted together — one of the reasons there are so many rhythm and time changes in Zep’s songs. It just feels too jerky-jerky to me. Also, I feel that Robert Plant’s vocals are the weak link in the group. Jimmy initially tried to recruit Steve Winwood and Terry Reid, either of whom had much better pipes. Robert was unique, just not always my cup of tea. I came to appreciate their musicianship, especially John Bonham’s drumming, but in the end, their behavior did me in. Sorry, but I believe that when kids buy your albums and come to your concerts, you owe them more than just showing up.

Before you began writing books you managed Bruce Springsteen. Did you give him any tips when he sat down to write his memoir?

I did not give Bruce tips for writing his memoir. I wouldn’t have dared. That guy is the most capable person I’ve ever met. That said, I think he left out a lot of great stuff that happened with getting the band off the ground. And he might have told the story about our two-week stand at Max’s Kansas City, when our opening act, Hall & Oates, walked off at the end of the first week and was replaced by a band none of us had ever heard of: Bob Marley & the Wailers — their first U.S. appearance. Think about it: three shows a night, six nights a week, in a room no bigger than a lounge: Bruce and Bob and their entire bands. What a week of music.

Do you give yourself short-term goals to keep your motivation up about progress on projects that last years?

No short-term goals for me. Just the big picture in cinemascope. I’ve taken on some big projects: Dylan, the Beatles, Julia Child, Ronald Reagan, and Zep, and they all seem to unspool at their own speed. I don’t worry about motivation because I love what I do. What a gift to be able to immerse myself in the lives of these extraordinary people! And I’m one of the few writers who actually enjoys the writing process. There is no blood on the keys of my computer. I’ve got the process pretty well compartmentalized. I only write in the morning. By 2 o’clock, I am done for the day. In the remaining hours, I read, cook, watch episodes of “MI-5,” and enjoy the benefits of living in two of the world’s great cities: New York and Los Angeles.

Do you transcribe your own interviews?

I transcribe all my own interviews — and I am whip-fast. I’m a musician, guitar and piano, and when I transcribe tapes, I think of them as symphonies and I’m playing along on the keyboard. Goes by fast. My wife’s also an author, and I do a lot of her transcriptions as well. She thinks I’m nuts, because I enjoy it.

How do you know when you have enough reporting to start writing? 

Strange how it evolves to where I begin to write. It always happens the same way: I simply wake up one morning and it dawns on me that it’s the day to start writing. I guess it’s just an internal thing. I’ve done the work and I know it’s time to move forward. Over-report? Well, I guess I did it with the Beatles, but I usually wind up with everything I need. Deadlines — they don’t exist for me. I tell my editors that they’ll get the manuscript when it’s finished, and for the most part they’ve played the game. (Although Little, Brown drove me nuts to get the Beatles’ bio in. I guess eight and a half years was stretching their goodwill as far as it would go.)

What is next for you?

Another great project. I just signed a contract to be the Rolling Stones’ biographer. And don’t ask me when you can expect the manuscript.