In the 11th year of his third (or is it his fourth?) creative peak, it’s pointless to talk about Bob Dylan outside of the context of the shadow he casts over the American musical landscape. The man is an institution, and, if he lives another 67 years, it goes without saying that critics will keep on leaning over one another to hear what new and indivisible truths he’s plucked from the ether and placed in his music. His last album, the vibrant and meditative “Modern Times,” cemented yet another victorious trilogy that began with 1997’s “Time Out of Mind” and 2001’s “‘Love and Theft.’” Now, Columbia Records issues the eighth installment of Dylan’s strikingly consistent “Bootleg Series,” called “Tell Tale Signs,” seemingly as a triumphal arch erected in honor of a last fruitful, if wearying, campaign. At two discs and over two hours (the deluxe edition features a third disc and a 150-page booklet to boot), “Tell Tale Signs” is yet another thoroughly enlightening, thoroughly rewarding, and thoroughly listenable rarities collection—this time, of Dylan’s vaunted latter-day catalogue, spanning the time from 1989’s “Oh Mercy” up until 2006’s “Modern Times.”

The quality of the songs collected here is worthy of that period’s legacy. Each disc begins with an alternate version of the surging, melancholic reflection “Mississippi,” originally found on “‘Love and Theft,’” and for a lesser collection it would seem impossible to match that song’s first moments. But Dylan succeeds in more unexpected ways as the album unfolds. Both versions of the gospel ballad “Dignity” manage to be moving, yet distinct from the other in arrangement and lyrical delivery. “God Knows,” an “Oh Mercy” outtake, harks back to the more propulsive, Hawks-driven days of Dylan’s 1960s height. More traditional outings like “32-30 Blues” and “Cocaine Blues” reintroduce the audience to a roots-oriented Dylan who, with his voice muted and weathered by age, seems almost a more fitting troubadour than the explosive, snarling youth that wailed on “Maggie’s Farm.” The live cuts are all supreme, though they favor recordings prior to his most recent tour—a much more subdued affair than is apparent on a rousing 2002 cut of “Lonesome Day Blues.”

To a certain extent, any release from the Bootleg Series is useless to all but the serious Dylan fan. Over the years, Dylan’s studio albums have evolved into institutions of their own—even that commercial joke and critical gaff, 1970’s “Self Portrait,” looms mythic in the catalogues of completists—and the Bootleg albums that deal explicitly with rarities and outtakes smack, to casual listeners, of revisionism and recycling. And to that same extent, those listeners are right. The man’s catalogue is simply too labyrinthine, too inscrutable, too fascinating to begin with anything but the undisputed classics: “Highway 61 Revisited,” “Blood On The Tracks,” or “Blonde On Blonde.” But for the serious Dylan fan, the Bootleg Series itself is not only a gift—it’s a necessity.

If we search for Dylan’s identity—in his evolving musical tableau, in his baffling lyrics, in his myriad influences or his harebrained interviews—we can never get closer to the mark than the knowledge that he is a man that seeks to please himself first. The Bootleg Series documents songs not only as they progress toward the final studio version (as is the case on “Tell Tale Signs”) but as they shift to fit the transformed psychology of their creator (as is the case on the sublime “Royal Albert Hall” recording). By releasing these tracks, not as bonus cuts to some cheapskate reissue of “Time Out of Mind” or “Modern Times,” but as their own document, Dylan seems to be challenging his audience, even baiting them, to believe that his songs are never done changing. Even by invoking the title, “the Bootleg Series,” he both seizes and relinquishes ownership of his work—is he bootlegging himself, pillaging his own legacy?

There is a troubling possibility that Dylan will never release another studio album. His career has flourished and faltered for nearly five decades, and no matter what 2009 or any other year has in store for Bob Dylan, his greatness will outlast many of the contemporaries of his youth, and even more of the contemporaries of today. But if “Tell Tale Signs” indicates an icon fading away, it’s unlikely that Robert Zimmerman, Blind Boy Grunt, Jack Frost, or whatever you want to call him could have picked more worthy music to accompany the falling curtain.

—Reviewer Ryan J. Meehan can be reached rmeehan@fas.harvard.edu.