With “Saltburn,” writer-director Emerald Fennell has put into the world something delicious, debaucherous and, at times, a little dopey.

Part vaguely absurd comedy and part twisted thriller, the latest effort from the promising “Promising Young Woman” filmmaker is a tale of obsession taking place during the mid-2000s within a world of the wealthy where beauty is overvalued.

In its opening moments, Oliver Quick (Barry Keoghan) tells us that everyone was in love with classmate Felix Catton (Jacob Elordi), but not him. Oliver protected Felix and, sure, he loved him, he says, but he was not IN love with him.

We suspect he is lying to us or, possibly, to himself.

Before the awfully awkward Oliver encounters the good-looking and charming Felix, he isn’t having a great time at Oxford University, mostly spending time with a truly weird student who proceeds to yell at Oliver when he initially declines to offer him a math problem to solve on the spot.

Soon, though, he is saving the day for Felix, offering him his bike to get to an appointment after Felix finds that his has a flat tire. Later, at a pub, Felix, having invited Oliver to drink with him and his friends, saves Oliver when he apparently can’t pay for a round when it is his turn.

The two grow closer throughout the school year — Oliver may never be as cool as Felix, but he hooks up with a girl, briefly, only because she hopes to make Felix jealous — and Oliver turns to Felix after receiving a distressing call from his mother. Hearing Oliver’s father has died, Felix does what he can to comfort his new friend.

He even invites Oliver to spend the summer with his family. Oliver arrives at what proves to be an estate called Saltburn, where the family members and guests live in a huge, castle-like home and are served by, among others, the intimidating, statuesque butler, Duncan (a delightful Paul Rhys).

Felix is happy to see Oliver, giving him a quick tour and offering him a room near his — they are connected, in fact, by a bathroom with multiple sinks and a tub in the center. (That tub will be the location of this often-wild film’s wildest moment, but that’s all we’ll say about that.)

Oliver gets to know the rest of the family — Felix’s mother, Lady Elspeth Catton (Rosamund Pike); father, Sir James Catton (Richard E. Grant); and sister, Venetia Cattan (Alison Oliver, “Conversations With Friends”) — and Elspeth’s hanger-on friend Pamela (“Promising Young Woman” star Carey Mulligan, who makes the most of her limited time). He already knows Felix’s cousin Farleigh Start (Archie Madekwe of “See” and “Gran Turismo”) from school, but the two have never really hit it off.

Oliver eventually finds his way within this odd micro-society, learning how to be a comfort to Elspeth but playing with fire with Felix by engaging in, um, certain activities with Venetia. He lies about them to her brother, as remaining close to Felix is Oliver’s primary concern. Farleigh never warms to him, by the way.

We won’t say much more about where the story goes from here, but we must say it’s hard to buy into a key premise of “Saltburn”: that Felix would have much to do with Oliver beyond, say, the kind aforementioned moment at the college pub.

In the hands of Elordi (“Euphoria,” “Priscilla”), Felix is effortlessly cool and, as portrayed by the talented Keoghan (“The Killing of a Sacred Deer,” “The Banshees of Inisherin”), Oliver is anything but. It’s hard to believe Oliver — strange in his mannerisms to the point of distraction — would fit in with the rest of the family. If we’re guilty of being too hung up on this given the film’s absurd leanings, so be it, but Keoghan simply seems wrong for the role as written.

Putting that aside, “Saltburn” so regularly is a riot of its own distinct kind that it should keep many viewers entertained.

We were left wanting more of the always enjoyable Pike (“Gone Girl,” “I Care a Lot”), especially as vapid Elspeth is given some of the movie’s best lines by Fennell.

Arriving during the holidays, the film is like a sugary but savory seasonal cocktail. There is almost no nutritional value here whatsoever, but it’s undeniably tasty. If nothing else, the scenery — both the place and the people — is there to be slurped up.

So soak it all in … but you may want to steer clear of that tub.

(“Saltburn” contains strong sexual content, graphic nudity, language throughout, some disturbing violent content, and drug use.)

“Saltburn”

Rated R. At the AMC Boston Common, South Bay Center, Causeway 13, Alamo Drafthouse Seaport, Landmark Kendall Square and suburban theaters. Grade: B