Like Starz’s “American Gods” before it, Amazon’s newest limited series attempts to adapt the philosophically lofty, theologically-infused work of British novelist Neil Gaiman. In his 1990 novel “Good Omens” (co-written with Terry Pratchett), an odd-couple angel and demon attempt to avert the apocalypse in order to continue enjoying their unusual partnership. Onscreen, this pairing — between a saintly being played by Michael Sheen and a fallen angel played by David Tennant, both seeking to save the world for their own reasons — is the best part of the new “Good Omens” limited series. But it’s not enough: This six-hour journey towards the end of time comes to feel grindingly slow by the end, more anticlimax than fight for Earth’s future.

We meet Sheen’s Aziraphale and Tennant’s Crowley at the very beginning of recorded myth, in the Garden of Eden. Their personalities shake out with crystalline clarity (fitting for the animate avatars of Good and Evil): Aziraphale trusts in God’s plan for the universe, even as it’s easy to draw holes in the logic, while Crowley can’t resist looking for malign intent in everything God does. Why, he asks, was the tree of knowledge placed in Eden in the first place, if Adam and Eve weren’t to eat from it? God herself (Frances McDormand in a voice-only performance) is gnomic and unknowable; her obliqueness is the point. And her agent Gabriel (Jon Hamm) is a nice guy but basically useless, interested only in burnishing his own image. Aziraphale and Crowley are left on their own as our guides to this universe.

They do well enough. The pair’s banter can be frustratingly stale — Crowley rejects being called “nice,” which he calls (wait for it) “a four-letter word” — or have one beat too many, as when Aziraphale meets a fellow divine creature whom he knew centuries before. “Yes! Sodom and Gomorrah. You were doing a lot of… smiting people. And turning them into salt.” (The point is made four words in; as is so often the case in this show, what follows is just showing off.) But their partnership, which Crowley openly acknowledges as a vexed but real friendship and which Aziraphale can’t acknowledge as more than a working relationship, drives the show forward.

It’s not a road without obstacles, though: The plot, here, is a mire, with the pair seeking to preserve their balance of power on earth by fighting off an Antichrist whose identity is, at first, concealed. We don’t know which child will bring about the end of days at first, thanks to a laborious game of three-card monte played with babies in a nunnery, one of whom will grow up to bring about the end of days — a device whose convoluted, showy nature gets at what makes “Good Omens” quite so frustrating. Much like “American Gods,” with its high-toned concept bearing little fruit in the way of plot or insight, this show feels above all relentlessly proud of itself, burnishing all it knows about religion and philosophy in service of a story that simply doesn’t move. To wit: One episode begins with a montage of Aziraphale and Crowley influencing humanity through history — at the building of Noah’s ark, at Shakespeare’s Globe. It’s a point that’s made so laboriously and repetitively that the opening credits drop some 28 minutes into the episode. Elsewhere, deities representing, say, War (Mireille Enos, doing her best) or Pollution (Lourdes Faberes) drop into and out of a story that didn’t strictly need them to bulk out its running time in the first place, and seems to have little real room for them as it stands.

Appetites for logic puzzles about the intentions of God and practices of worship will vary. After having known some philosophy majors my freshman year of college, such debates evoke in me a prickling desire to leave the room as soon as I can. But my openness to a show with two charming, underplayed performances at its center working through such a complicated thing as partnership with one’s ideological opposite was real, and it faded as the hours of increasingly exhausted showmanship and patter about religion wore on. In cramming in quite so much incident and varyingly successful attempts at humor, “Good Omens” traverses a great deal of ground. That it ends up saying so little feels like a missed opportunity.

“Good Omens.” Amazon, May 31. Six episodes (all screened for review).

Executive Producers: Neil Gaiman, Douglas Mackinnon, Chris Sussman, Simon Winstone, Rob Wilkins.

Cast: David Tennant, Michael Sheen, Jon Hamm, Frances McDormand, Nick Offerman, Jack Whitehall, Miranda Richardson, Adria Arjona, Michael McKean, Anna Maxwell Martin, Mireille Enos.