When the five members of Fleetwood Mac reconvened in the studio in 1978 to record the follow-up to their massively successful/decade-defining/inescapable disc Rumours, it would have been painfully easy to simply spit out Rumours II.

Instead, they took 13 months and spent a then-unprecedented $1 million-plus to birth Tusk, a double album of 20 songs spanning 72 minutes. The effort defied expectations, confounded some fans, sold “only” 4 million units, and produced only two singles resembling hits: the tribal-sounding title track (recorded with the 112-piece University of Southern California Trojan Marching Band), and Stevie Nicks’ ethereal “Sara.”

However, a funny thing happened with Tusk in the ensuing 35 years. Its standing among both Mac fans and musicians has skyrocketed, as has respect for the wildly diverse songs and experimentation. Now, Rhino/Warner Brothers has released Tusk: The Deluxe Edition. The 5-CD/2-LP/1-DVD set includes the original album remastered, a bevy of outtakes and alternate takes, and plenty of live material from the ensuing tour.

In the booklet of liner notes and rare photos, Jim Irvin celebrates the potpourri grab bag of music, spearheaded by Lindsey Buckingham’s newfound infatuation with the sounds of punk and New Wave music, and a desire to not repeat the same old formula. He would even adopt an entirely new look for the photos shoots and tour of closely cropped hair, suits, and…uh…heavy makeup.

“Listening to Tusk is like walking around a ridiculously eclectic art gallery curated by someone who’s keeping their aesthetic a secret,” Irvin offers. “And old master next to an abstract, a kinetic sculpture next to a watercolour. It makes no sense at first.”

Though, contrary to the established Rock History Narrative of him fighting for the change alone, both Nicks and Mick Fleetwood and not just Buckingham were also eager to shake things up, according to their own comments today.

And what of the effect as a whole? Buckingham certainly brings an un-Mac-like tension, nervous energy, and biting sarcasm to efforts like the deranged square-dance sound of “The Ledge,” the punkish “What Makes You Think You’re the One,” the biting “Not That Funny,” and the “rockabilly on acid” of “That’s Enough For Me.”

Stevie Nicks, always given something of a short shrift in terms of songwriting since she doesn’t play an instrument (not counting the tambourine), offers some of her finest work in the longing “Storms,” an upbeat “Angel,” elegiac “Beautiful Child,” and mysterious “Sisters of the Moon,” which surprisingly resurfaced on the set list for the Mac’s recent reunion tours.

Only Christine McVie’s contributions seem slight and listless — both lyrically and musically — save for some soft-and-gentle work on her usual romantic balladry in “Over and Over” and “Brown Eyes.”

Tusk's recording period saw Christine’s involvement with both Grant Curry (the band’s lighting director) and Beach Boy Dennis Wilson, while Buckingham fell into an intense involvement with record-company exec/former model Carol Ann Harris (who later wrote a not-that-flattering book about the relationship, Storms).

The shocker, fans later found out, was the news of Nicks and Fleetwood’s brief-but-intense involvement. It led to Fleetwood’s divorce from Jenny Boyd…who had previously had an affair with previous lineup guitarist Bob Weston…and was the sister of Rock’s Greatest Muse, Pattie Boyd, who sent both George Harrison and Eric Clapton into romantic bliss and yearning, poured out on vinyl.

And when Nicks and Fleetwood’s involvement ended, Nicks’ best friend, Sara Recor (partial inspiration for the song), took up with Fleetwood without either bothering to tell Nicks about it, which crushed her (are you following all of this?).

Thus, Nicks admits today that a number of her songs are about Fleetwood, and it’s not hard to interpret many of hers and Buckingham’s lyrics as continued musical snipes and judgments on their relationship.

Of the demos and alternate versions, there’s some very interesting development chronicled in the songs “I Know I’m Not Wrong” and “Tusk” as Buckingham — like he did with much of the material — tinkered with them in his own studio extensively before bringing them to the band. It was a way of songwriting that gave him more control, but which the band agreed to abandon after Tusk.

And on the live discs, listeners will find a band surprisingly willing to take risks with tempos and delivery onstage with material recorded in studio. And that includes tunes from their previous two records, Fleetwood Mac and Rumours.

So, while the hefty Deluxe Edition of Tusk may be for Mac Addicts only (and those with record players), less expensive options included a 3-CD Expanded Edition and a 1-CD Remastered effort.

In either case, for what attention and sometimes derision it received on release, Tusk is the one effort in the band’s discography whose standing has improved with time. Oh, and the meaning the title? It was Fleetwood’s slang term for a penis. You’re welcome for that.