Music writer Giles Smith was a 12 year old boy staying up past his bedtime 50 years ago to watch ABBA slay Eurovision with Waterloo.
That night would kick off a lifelong infatuation with the Swedish pop titans, even though, he says, in the 70's it was uncool for teenagers to love them.
His new book seeks to understand the nature of hit songs through the ones they produced with great consistency and the global longevity of a band that hasn't performed together in 42 years.
His book is called My My! ABBA Through the Ages.