Benji Wilson

Special to USA TODAY

WEYBRIDGE, England — Jon Hamm, dressed in fine cashmere head to toe, is looking at his feet and sees his own face reflected.

“I guess everything in heaven is probably this shiny,” he muses.

He’s waiting for a take, staring at himself in the distractingly reflective silver floor of a high-tech, disused office block formerly occupied by the electronics giant Samsung. Today it’s heaven, a key location in Amazon’s big-budget adaptation of Terry Pratchett and Neil Gaiman's apocalyptic comedy-drama "Good Omens" (out Friday).

Hamm plays the angel Gabriel, but in Pratchett and Gaiman’s world he’s a sort of overbearing line manager: “He’s the boss that everyone has, but everyone hates – he’s constantly smiling and telling you ‘great job!’ while also subconsciously saying ‘you’re terrible,'” says the actor, who's best known for "Mad Men."

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On set, Hamm is micromanaging Michael Sheen, who plays one of the series’ two lead roles, a subordinate cherub named Aziraphale. You get some idea of the series' tone from a brief conversation in which Gabriel upbraids Aziraphale for having "lost" the Antichrist. It's vintage Pratchett, who wedges the biggest questions next to the most mundane realities, and it will appeal to his many fans. Just before director Douglas Mackinnon ("Sherlock") yells "action," a man dressed in white scoots by on a hoverboard.

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“Is that in the script?” Hamm asks. Nervous laughter. No one seems quite sure.

This exquisitely arch series is, in some way, one of Amazon's most original. "Omens" tells the story of Aziraphale and Crowley (David Tennant), an angel and a demon, who've been on Earth since the Garden of Eden, working for their opposing teams in heaven and hell.

One is charged with lighting fires, the other with putting them out. Yet over the centuries. they've become friends. We meet them as the antichrist is being delivered to Earth – one of Crowley’s missions is to ferry the demonic babe to the maternity ward. But they both realize this means the end of humanity as we know it and, as Tennant puts it, “Crowley and Aziraphale have quite a nice time on Earth. They quite enjoy the dinners and the wine and the lifestyle.”

"Good Omens" has been a momentous undertaking: a story that takes in all of Christian history in six hours of heavy theology and wry humor has a lot to accomplish. The third episode features a sequence that follows Aziraphale and Crowley from their first meeting at the Garden of Eden to reunions at Noah’s Ark, the Crucifixion, ancient Rome, Shakespeare’s Globe Theater, the French Revolution, two World Wars and in the present day. It’s all done in less than 20 minutes.

Unsurprisingly. that kind of time travel has taken the better part of two years to film – plus another 30 if you include several cinematic misfires. Immediately after it was published in 1990, "Good Omens" was planned as a movie from Terry Gilliam ("Monty Python") that led nowhere in the way that only Terry Gilliam’s movies can. That was before Pratchett, fading from Alzheimer’s disease, told co-author Gaiman that he wanted a TV adaptation of the novel to be made. It became practically a last request.

“He wrote me a letter – he’d never written me a letter before,” says Gaiman, the head writer and executive producer. “He said, ‘You’re the only other person out there with the same love and understanding and passion for this that I have. I know how busy you are, but I want to see this before the darkness takes me. Will you do this, please?’ In 35 years, he’d never asked me anything before. So I said yes. And then he died,” in 2015.

That leaves "Omens," a series of manifest quirk that will irk some and delight others, as both a tribute to Pratchett and a gift for his many fans.

“I'm trying to make the show that Terry would have loved to have seen, had he lived,” Gaiman says. “It’s just love and respect for the material – on a weird level it’s suddenly become a matter of trust.”