The eighth instalment of Dylan's Bootleg Series covers the years spanning his 1989 return to form with Oh Mercy up to the present day.

During this period he managed to conquer a long-standing blight of writer's block, establish himself as the pre-eminent repository of American roots-music forms, and ultimately find the route to the Indian summer of Time Out of Mind, "Love and Theft" and Modern Times.

It's a remarkable collection, as racked with doubt and disillusion as one might expect, yet defiantly exposing the vulnerabilities and irritations that provoke pearls such as "High Water" and "Ain't Talkin". The former is featured here in a tremendous live version, funky and fetid, the kind of re-imagining that sustains fans through years of fallow performances, while the latter landmark, the singer's most absorbing State of the Union address for years, is delivered with more swagger than the Modern Times version, Dylan not so much walkin' as struttin', the song taking on a new character, more purposive than reflective.

That's perhaps the most radical example here of the way Dylan's art is kept constantly in flux, the illumination of which is the greatest virtue of the Bootleg Series. The alterations of lyrics, tempi, arrangements and delivery re-cast these songs as refracting prisms, whose meaning changes according to where the light hits. Take the simple, more urgent solo version of "Most of the Time", which could be from Another Side Of were it not for Dylan's deeper vocal intonation.

Or the various interpretations – from brusque and aggrieved to gently cajoling – which alter the aspect of "Dignity": it's substantially the same song, give or take a line or two, but each time he approaches the mic, Dylan seems to see it in a different light. Sometimes, that light suggests a song's just not right for the project in hand – rather less with "Dignity" than with its fellow Oh Mercy orphan "God Knows", which even in its original form is clearly more appropriate for the nursery-rhyme-styled Under the Red Sky.

Another great Bootleg virtue is its unearthing of classic songs quixotically left off albums or shunted on to soundtracks. They include "Cross the Green Mountain", a Civil War epic of bitter resignation whose melody recalls "Sad Eyed Lady of the Lowlands" but whose fiddle arrangement recalls the Rolling Thunder years, and a couple of outtakes from Time Out of Mind, the love ballad "Red River Shore", and most intriguing, "Dreamin' Of You", where ghostly guitar and organ ride a spry New Orleans drum lick as Dylan offers sardonic commentary on his life: "For years, they had me locked in a cage, then they threw me on to the stage. Some things just last longer than you thought they would."

Pick of the album: 'Ain't Talkin', 'Dreamin' of You', 'High Water', 'Cross the Green Mountain', 'Red River Shore'

(Columbia)