This 1966 file photo shows The Beatles on their trip to the United States and Canada. [Photo/Agencies]

No matter how much you think you know about the Beatles, Mark Lewisohn probably knows more.

Hundreds of books have been written about the band, but none with such care and authority as those by the 58-year-old British author.

His resume includes comprehensive releases on their concert performances (The Beatles Live!) and studio work (The Complete Beatles Recording Sessions), for which he was given a Beatles obsessive's dream job, getting paid by EMI Records to enter the inner sanctum of the Abbey Road studio and listen to the band's recordings.

"I was a researcher and realized that the books (on the Beatles) were not quite as well-researched or written as I had expected them to have been," he says, explaining how he evolved from fan to author.

"One project led to the next and suddenly I found myself with a career as a writer, which I hadn't actually intended."

Lewisohn is in the midst of a three-volume biography of the Beatles and most recently contributed text for a coffee-table book about their landmark 1964 film, A Hard Day's Night.

Here, in an interview, he talks about A Hard Day's Night, the Beatles' lasting appeal and the joys of Beatles scholarship:

Why A Hard Day's Night was so much better than movies starring other early rock stars?

As consumers, The Beatles knew those films were rubbish. They hated them. They recognized them for what they were, which was transparently flimsy and knew that should the occasion ever arise when they would be offered a film that they had to be very careful about saying yes.