Today, I know a lot of people who have pictures of Bob Marley on their walls, but wouldn't dream of playing one of his records. Or kids who know who he was and what he stood for, can even quote bits of his lyrics, and have never knowingly heard a Marley song. What Bob Marley left to the world will always be far more powerful and durable than a few LPs. Bob Marley, perhaps second only to Nelson Mandela, is the greatest of the Third World Superstars, but those who know his music well are probably as rare as those who've read The Long Walk To Freedom. In this context a book dedicated to Marley's 'musical legacy' is in danger of missing the point. Happily, Bob Marley: His Musical Legacy doesn't.

Given Bob Marley's global profile and the collectability of vintage reggae records, the most surprising thing about this illustrated book by Jeremy Collingwood is that it took so long to come to pass. But then, given the exhaustive attention to detail, the range of marvellously reproduced original records, record labels and record sleeves and the wealth of previously unseen or long-forgotten photographs, the 20 years Jeremy Collingwood spent putting this work together doesn't really seem all that long. Indeed Collingwood has gone one better than merely cataloguing Marley's entire musical output: he's described each song, and brought his reviews to life with product illustrations, period photoraphs and memorabilia.

Essays and visuals tell the fascinating backstory of the early Jamaican record industry and the unique 'push-pull' situation that gave birth to it, as the producers struggled to do things their way – the unique Jamaican social, aesthetic and economic world of the sound systems – while being culturally colonised by the USA. Marley's own career, from crop-haired copycat crooner in the Curtis Mayfield mould, to dreadlocked symbol of a unique Jamaican cultural vitality which itself went on to colonise the world, captures the essence of the whole story.

Collingwood brings a different vibe to the Marley industry by devoting more space to the artist before he became an international rock icon than after he was famous. In spite of this being almost a necessary state of affairs in a discography-type tome such as this – there was much more, and many would agree much more interesting, music from Marley before 1975 – it wouldn't have been all that surprising had he taken the more populist path. Especially with the word 'legacy' in the title.

Marley's legacy was never musical. Spiritual? Certainly; humanitarian? Absolutely; and internationalist? Indeed. But even the most generous-minded soul would be hard pressed to name two acts, that didn't involve any of Bob's children, with any obvious or deliberate Marleyisms in their music.

Marley began his career in a vocal trio, The Wailers, with Peter Tosh and Bunny Wailer. The Wailers' music was largely formulaic cod-American soul, generic ska or mildly interesting roots reggae, the best of which, like the sessions produced by legendary eccentric proprietor of Black Ark studios Lee 'Scratch' Perry, say as much about the producer's genius as that of the singers. Similarly in the years leading up to his death from cancer in 1981, though highly feted and a global superstar, his musical output amounts to half a dozen singles, not all of which were original.

Artists from Sinead O'Connor to Beenie Man vociferously cite Bob Marley as an inspiration, but they are rarely referring to his actual music. And this is where a book like this is so useful in honestly assessing Marley's life. It lays out his entire musical output in an easily taken-in form, then puts it into some social/political context, and allows the comparisons and assessments of the records to be made in such a way that permits real understanding of what Marley had to do in order to achieve what he did.

Marley made his mark by cleverly morphing his reggae into some sort of exotic rock music. But always on reggae's terms: he established a clearly identifiable rock group state of affairs on stage; he carried a guitar as a prop as much as a musical contribution; he shook his locks in a creditable approximation of rock-star long hair; and flattened out the beat to an arena-friendly, easy-to-follow one drop.

What was he trying to tell the world? Most importantly, his views on injustice had evolved beyond exclusively Jamaica and his own black people to include the oppressed of all races all over the world. He was driven to take his message – of the need to struggle against hypocrisy and corruption, to stand up for yourself and combat oppression – to a global audience. He also, of course, was the global symbol for his religion, Rastafarianism. He had switched from the hard line Nyabinghi Rastafari to the far more all-embracing Twelve Tribes – the former was strictly black, the latter offered a proto-hippie rainbow culture approach – which suggests that no matter its visibility and the attraction of Rasta's counter-cultural symbols – the locks, the spliffs – the core message was universal, about human rights, fairness, dignity, rather than doctrinal or dogmatic. The simple appeal of words like these from 'Redemption Song' – "Emancipate yourselves from mental slavery/None but ourselves can free our minds" – reached out to all, required no religious obeisance and confirmed his position as a transcendent global statesman.

Maybe the later music was simplistic. Yes, some of the later lyrics were heading towards sloganeering which could too easily become the soundtrack to a self indulgent global hippiedom – "everything's gonna be alright", "no woman no cry" – but these were necessary tactics to disseminate the message: that we all ought to be a bit nicer to each other.

That was the legacy.