David Bowie's long-time friend and producer Tony Visconti said the late singer's final album - released two days before his death - was "his parting gift" to the world.
Blackstar became available to buy on Friday, the day he turned 69, with its lead single, Lazarus, opening with the lyrics: "Look up here, I'm in heaven."
Little was known about Bowie's ill-health, although Visconti - who produced the star's music dating back to the 1960s - hinted at questions over his mortality.
In a Facebook post, he said: "He always did what he wanted to do. And he wanted to do it his way and he wanted to do it the best way.
"His death was no different from his life - a work of art.
"He made Blackstar for us, his parting gift.
"I knew for a year this was the way it would be. I wasn't, however, prepared for it.
"He was an extraordinary man, full of love and life. He will always be with us.
"For now, it is appropriate to cry."
Blackstar is full of symbolism that suggests he knew it was time to say goodbye.
The singer's 25th studio album, which came out on his 69th birthday with just seven tracks, was the first that did not feature his photo on the cover but instead a black star.
The album's lyrics are, as always cryptic, but posthumously poignant. Lazarus, released on December 17, opened with: "Look up here, I'm in heaven, I've got scars that can't be seen, I've got drama, can't be stolen, everybody knows me now." It ends with: "Just like that bluebird. Oh, I'll be free. Ain't that just like me?"
The video for Lazarus - named after a biblical character who was raised from the dead by Jesus four days after he died - is also full of images that could allude to death.
Bowie features as a tormented blind man with buttons for eyes on a bandage over his own eyes. The video is bleak and dark in colour - much like the title track Lazarus.
The video for Blackstar opens with a dead spaceman with a skull - a symbol for death - on his space suit.
The lyrics also allude to death: "Something happened on the day he dies. Spirit rose a metre and stepped aside."
One fan wrote under the video in an online forum: "I believe the scene with the spaceman and the scene with the solitary candle are connected. The candle represents illumination in darkness and so does the spaceman. In the next scene with Bowie we see him without the blindfold and looking forward, possibly found his purpose?"
The outro of the penultimate song of the album Dollar Days repeats: "I'm dying to. I'm trying to," as the music fades.
Twitter user Andy Levy said: "Listening to 'blackstar' (again) and oh man the lyrics on a bunch of the songs take on whole new meanings knowing what he was going through."
On the final track I Can't Give Everything Away, Bowie sang: "I know something is very wrong, The pulse returns the prodigal sons, The blackout hearts, the flowered news, With skull designs upon my shoes."
The album received a thumbs-up from most critics including the Independent, which called it "the most extreme album of his (Bowie's) entire career".
On Twitter Hunter Felt said: Seriously. It's very clearly his goodbye album."
Asked about symbolism in November, John Renck, director of Bowie's short film Blackstar, told Vice magazine: "Most things like this are for the eyes of the beholder, you know? You make of it whatever you want. What I can say, on one side of things there is no deliberate, underlying, firm quest to have any references to past times."
