It's a gentle, easy-going 1950s comedy. Kim Novak belongs to a coven of witches in Manhattan. She puts a spell on neighbor Jimmy Stewart out of boredom but eventually falls in love with him, losing her powers. See, witches are permitted to have "hot blood" but not love. Elsa Lanchester is Novak's aunt, also a witch. Jack Lemmon is her brother, ditto. Hermione Gingold is the chief witch, and Ernie Kovacks is Sidney Redlich, an author who specializes in writing about witches.
I described it as a 1950s comedy because it could hardly be mistaken for anything else. Everything is so smooth and polished, from the set decoration, through wardrobe and plot, to the performances and direction. Take the character of Ernie Kovacks. He's referred to as "a drunk and a nut." And here's how the movie demonstrates these traits. He asks for a second drink, and, though he always wears a jacket and tie like the other gentlemen, his hair is a bit long and tousled. That's a strictly 1950s version of a drunk and a nut. Nothing is out of place; everything is tidy and free of dust. The soles of Jimmy Stewart's shoes are barely scuffed.
And the Zodiac Club, where the witches hang out. It's called "a low dive." Yet it's a clean, dark place with polite waiters, a quintet of musicians, neatly dressed clientèle, and potted plants against bare brick walls. That is not my idea or yours of a "low dive" -- not even for Greenwich Village in 1958. My idea of a dive in Greenwich Village is Julius's or The White Horse Tavern or The San Remo or The Swing Rendezvous, a now defunct lesbian hangout. The Zodiac Club is a high dive compared to these.
The kookiness we always hear about is muted by today's standards. I mean, Kim Novak is odd because she runs around her apartment in her bare feet. And she wears a lot of black clothes like the Beatniks of the period did.
But never mind all that. It's an enjoyable romantic comedy. Kim Novak is effective as Gillian, who runs a primitive art shop for the uptrodden. She has a strange beauty, bulky and ethereal at the same time. She glides rather than walks, a wispy presence. Her eyebrows seem drawn with a set of plastic French curves. And Jimmy Stewart is quite good as the bewildered and bewitched victim. In the 1930s he usually played in light roles. In the postwar years and for much of the 1950s he was the tortured protagonist, but here he puts his early experience in comedy to good use. Who could resist laughing when Hermione Gingold forces him to wear a shawl and drink a hideous concoction of putrid fluid in order to cure him of Novak's spell? It's good to see him as a stooge instead of the angry and indignant man of principle he was in danger of becoming. Richard Quine directs the movie quietly, without fireworks or special effects, and does some interesting things that the play couldn't have had. Note the scene in which Novak casts the spell over Stewart, when the Siamese cat's face and ears seem to merge with Novak's startling eyes.
Ernie Kovacks in the 1950s was a well-known television personality. There was never anything quite like The Ernie Kovacks Show before -- or after. It brings the word "surrealism" to mind. He could stage five minutes worth of wordless and indescribable tricks in an unpopulated room with only Bartok's Concerto for Orchestra as background. And he did an unimpeachable sketch using the character of Percy Dovetail, an effete poet. The credits kind of skip over The Condoli Brothers but that's rather casual because these two guys -- Pete and Conte -- were virtuoso trumpeters with independent careers in jazz ensembles. Conte was later a member of Doc Severison's band on Johnny Carson's Late Show.
The third act kind of bogs down a little and becomes more "romantic" than "comedy". But it's never dull. The whole film rolls along as neatly as Van Druten's play and the kids will probably get a kick out of it too.

In a nutshell: this is a cookie cutter romantic comedy that really WANTS and TRIES to be something more. It wants to be Harold and Maude, Annie Hall, The Graduate. It wants to be deep and human. It has interesting camera shots, lighting, music, editing, all of which give it the feel of an important movie. The dialog is smart -- at times. There are some "laugh out loud" moments.
But here's what keeps it from ultimately being anything more than a formulaic late-night-cable, in-flight, time-killer:
1. David Schwimmer -- how many times can Joe sad-sack puppy dog stare blankly into space with his jaw hanging open before it starts to get annoying? Maybe some drool would have helped.
2. Gwenneth Paltrow -- she's really flat here and not just in the chest. Her role is supposed to be this lively, nice, caring girl who just keeps getting herself into wrong situations, is very confused as a result, and that is why a sad-sack loser like Schwimmer has any chance with her. But Gwenneth plays her very dull. Combine this with puppy-dog drool-face (above) and you have very little chemistry to care about.
(I kept picturing someone else in this role -- Kate Hudson for example.)
3. The script and the plot -- the stuff that happens just basically doesn't ring true; all the problems get wrapped up in the end with such a neat and tidy bow on top that it seems like a whistle blew and the script writers just said "oops, time to wrap it up, got a train to catch!" So they pulled out the Hollywood formula book, checked off all the boxes, and went home.