Seeking Major Tom, William Shatner’s new double-disc concept album, is about as ambitious as covers collections get. Stringing together 20 sci-fi themed classics into a loose narrative about the voyage of David Bowie’s Major Tom, it also features an absurdly eclectic roster of collaborators, from Lyle Lovett to the MC5’s Wayne Kramer, Tangerine Dream’s Edgar Froese and funk legend Bootsy Collins.

No surprise, then, that the album is about as polished as it gets, musically, with production to match. And Shatner’s delivery is as idiosyncratic as ever, reciting lyrics with little regard for such banalities as melody or rhythm.

But for all that, Seeking Major Tom can’t help feeling like a step backwards for the octogenarian actor. His last album, 2004’s Ben Folds collaboration Has Been, was surprisingly heartfelt, funny and generally better than it had any right to be. Seeking Major Tom, in contrast, comes off as a lark, a retreat to the misunderstood (but admittedly hilarious) covers that started his musical career, just with Shatner in on the joke this time.

Sometimes the camp works, as when Shatner and Collins see who can get goofier on “She Blinded Me with Science.” Sometimes, it’s just painful — “Bohemian Rhapsody” was melodramatic enough to begin with, thanks. But while it’s good to know that Shatner could sub in if Lou Reed ever walks out on his Metallica collaboration (seriously, just listen to his take on “Iron Man”), Seeking Major Tom’s finest moments are those where the actor seems to take things more seriously, as in Kurt Weill’s “Lost in the Stars,” or a surprisingly effective take on “Rocket Man.” We all know Shatner does irony well, but it’s the moments of sincerity that work best.