Keith Badman couldn’t have timed it any better.

The London-based writer’s very-thorough “The Beach Boys: The Definitive Diary of America’s Greatest Band on Stage and in the Studio” (Backbeat Books) is expected in stores on Oct. 15, just as Brian Wilson’s nearly 40-year masterpiece, “SMiLE,” finally sees the light of the day.

“Brian Wilson Presents SMiLE,” released on Sept. 28 by Nonesuch, is so awe-inspiring, it even has long-winded rock critics at a loss for words. Fans have taken notice, too, pushing “SMiLE” to a Top 20 debut on Billboard’s pop chart this week.

The Beach Boys are the most successful rock band in U.S. history, making it all the more shocking to hear that Badman’s original publisher rejected this ultimate, 399-page study of the surf-music icons. In a recent e-mail, Badman – the author of three books on the Beatles – touches on the California boys and more.

Pause & Play – How do you approach a challenge like this?

Badman – “With a lot of dedication and enthusiasm. I set out to do the definitive book on The Beach Boys and I sincerely hope I delivered that.”

P&P – Typically, how long does it take to piece together a book like this?

Badman – “I worked on this book for almost three years. But strangely, it never seemed that long. I enjoyed working on it immensely.”

P&P – Why did your original publisher reject the idea of doing this book?

Badman – “Because they thought a book like this on The Beach Boys would never sell. They didn’t believe there was enough interest in the group and their music.”

P&P – What’s the most underrated Beach Boys song?

Badman – “Too hard a question. Ones that spring to mind include ‘Time to Get Alone’ (which is superb) and ‘You Need a Mess of Help’ (which is just totally marvelous).”

P&P – What is perhaps the most overrated?

Badman – “None of them. As you’ll guess, I think The Beach Boys’ music is just wonderful.”

P&P – What’s your favorite BB song and album?

Badman – “Of course, I have to say the ‘Pet Sounds’ album but also ‘Sunflower’ from 1970 is a personal favourite of mine, along with ‘Holland,’ ’20/20,’ ‘Carl & The Passions,’ etc. etc. I’m too big a fan to choose, I guess.”

P&P – Who’s the most overlooked group member?

Badman – “A good question, but one hard to answer. I guess Dennis didn’t get enough recognition in the group. His music was really exceptional. I also think that Ricky Fataar and Blondie Chaplin’s short-lived input into the band in the early 1970s has been overlooked. I hope my book puts that right.”

P&P – As a session drummer yourself, how do you rate Dennis Wilson among the greats of the rock era?

Badman – “He was a great dummer. No doubts about it. Watch archive footage of the group on shows like ‘The TAMI Show’ and you’ll see he could really swing and keep a great beat. Underrated, I have to say.”

P&P – Have you heard Brian Wilson’s “SMiLE”?

Badman – “I really love it. It’s a truly superb album. If you enjoyed ‘SMiLE’ the concert, you’ll certainly love ‘SMiLE’ the album. It’s good enough to play again immediately after you’ve just listened to it. Brian Wilson is a musical genius!”

P&P – What are you working on next?

Badman – “Ah, another good question. I’m a little superstitious about publicly announcing anything until I’ve actually signed any contracts to do the work. But don’t worry. You’ll be the first to know.”