Paul Giamatti’s stack-blowing skill borders on the supernatural. Lips quiver, eyes dart for an escape he’ll never find and his jittery voice cracks until his patience evaporates in a profane eruption.

When it came to hitting the ceiling, Miles Raymond of 2004’s Sideways represented Giamatti’s Sistine Chapel — a divorced, flabby, middle-aged English teacher able to discern when Barely Legal isn’t “the new issue” and whose fine-wine enthusiasm masks borderline alcoholism.

A natural fit for a romantic comedy — or at least one from director / co-writer Alexander Payne, fascinated by the emotional muck of people past their prime.

Miles and actor pal Jack (Thomas Haden Church, never better) drive to California wine country for a weeklong getaway before Jack’s wedding. There, Miles finally pursues Maya (Virginia Madsen), a waitress he’s fancied, as Jack foolishly sleeps with her single-mom friend, Stephanie (Sandra Oh).

Sideways is about wine aged to perfection sipped by men who’ve aged to mediocrity — softer, hornier versions of Walter and The Dude. But Miles’s brutal honesty is its soul. He’s annoyingly, depressingly out there, but never fraudulent — unlike Jack, whose foolhardy libido incites comic scenarios both riotously funny and unexpectedly grotesque.

In other hands, wine-as-life metaphors might feel as refined as Mad Dog 20/20. But Giamatti and Madsen’s expressions, cadences and pauses possess that warm rush of realized love. Miles and Maya could go everywhere or nowhere, but she’s as close to peace as Miles will get. For somebody so low for so long, plateaus might as well be peaks.