Sunday morning, September 2015. Cerys Matthews is on the radio. She's playing a track by French-Lebanese singer and composer Bachar Mar Khalife. It's a soft, whispery mix of hushed, humming vocals and dropping piano notes. And beautiful.

It's possible, well, probable, that you've not heard it before. Already this morning Matthews has played Elvis and Ricky Nelson and the Big O and Van Morrison and Cream and Johnny Cash and Asha Bhosle. There's more to come before she finishes broadcasting. New sounds. Old sounds. Obscure sounds. Anything goes. Par for the course on BBC 6 Music at the weekend these days.

How can we define such an approach? Peelian might be a good working adjective. Because there was a time when this model – a willingness to mix reggae with rhumba, dubstep with doo wop, punk with poetry – was operated solely by John Peel.

It's now almost 11 years since Peel died while on holiday in Peru, a decade and more in which he has been posthumously accepted as the music curator par excellence, an acceptance that was not always forthcoming during his time as a BBC broadcaster.

These days he has an annual lecture named in his honour, a stage named after him at Glastonbury and a radio station that uses his example as its default setting. These days, too, he has 600-page books written about him.

Good Night And Good Riddance is a leisurely, amusing, at times bitty, often discursive, sometimes partial but always hugely entertaining ramble through Peel's broadcast history. David Cavanagh, who previously gave us a huge history of Creation Records, has listened to Peel shows stretching back to July 12, 1967 – The Perfumed Garden show on Radio London, with Donovan, Howlin' Wolf, The Jimi Hendrix Experience and Roger McGough all on the playlist – and forward to a few months before the DJ's death. The shows then become the structuring principle.

At first glance it seems a nerdy idea. But it works rather well. The show-by-show approach allows Cavanagh to circle around and tease out themes and continuities and the odd radical disjuncture. As a result we get an insight into Peel's changing tastes and attitudes, both musical and social, over the years. His changing accent too.

Over the years his support may have helped nurture the nascent careers of Bolan and Bowie and Rod Stewart and Siouxsie Sioux and Jarvis Cocker and Mark E Smith and The White Stripes among others. But that never seemed to cut much ice with his employers.

And so time and again, Cavanagh's narrative concerns itself with Peel's very marginality. A broadcaster packed off to inhabit air time on Saturday afternoons opposite the football or pushed to the edge of the daily Radio 1 schedule when few Radio 1 directors ever bothered to listen.

Peel, of course, flourished at the edges. It meant he could always play the sarcastic cheeky boy at the back of the class, ignoring notes from teacher and pretty much playing whatever he liked, from death metal by the charmingly named Arsedestroyer (nice, and not the worst – there are other band names not to be repeated even in such a liberal institution as this) to the candy-coloured pop of Altered Images.

Somewhere in his contrarian miserabilism, Cavanagh argues, hid a broadcaster firmly in the Reithian tradition, committed to the notion of informing, educating and entertaining (even if the last might have at times been something of an optional extra, depending on your capacity for death metal and hardcore Berlin-label techno).

Peel, Cavanagh convincingly argues, directly or indirectly had a huge influence on the nation's musical tastes. Or at the very least, he was an enabler for some major acts and movements. That said, it should be noted that while Bolan and Bowie quickly forgot their debt to Peel when they became successful, they also became greater artists too. The records they made post-success and post-Peel sessions were better than the ones they made when they came under Peel's wing.

Still, Peel's influence was huge musically. But did it stretch, as the book's subtitle suggests, beyond that to shaping Britain itself? That does feel a little like publisher's hype to be honest. Possibly closer to the truth is that you can see social trends pulsing through Peel's programmes; from the rise of the hippy counterculture to the snarl and spit of punk and the doomy nihilism of post-punk birthed under the shadow of what seemed like certain nuclear apocalypse (these days the fear has gone but the bombs are still there, curiously enough).

Cavanagh inevitably spends page after page during the 1970s cataloguing the default misogyny of rock bands, its fuzzy-around-the-edges (and that's being generous) legality too. "Rock stars are in no doubt," Cavanagh writes about Robert Plant's attitude towards underage groupies "any damage that these girls suffer is brought upon themselves." How much pain and horror can we now fold into that casual attitude? (By the by, when I interviewed him a few more months before he died. Peel described his first marriage in America to Shirley Anne Milburn, who was then 15, as a "mutual defence pact".)

The past is a foreign country, etc, etc. One in which as late as 1982 Peel could play a track by a Norwich band called The Crabs entitled Rape Rap and no one – neither DJ nor the band which included three women – saw that as problematic. Then again, where do we stand on the lyrics of Robin Thicke's 2013 number one Blurred Lines these days?

All of this is in play in Good Night And Good Riddance. And the result is anything but a hagiography. What it is, instead, is a singular take on a singular broadcaster. If you ever tuned in to record a Tools You Can Trust Peel session, this book is for you.

Good Night And Good Riddance: How 35 Years Of John Peel Shaped Modern Britain by David Cavanagh is published by Faber Books, priced £20