The first production of Howard Goodall and Stephen Clark's chamber musical version of the mawkish Erich Segal movie about a girl dying from leukaemia was all-white. Sasha Regan's Union revival is almost all-black, with rain and umbrellas at the funeral in the opening number.

Good idea, eh? Musical theatre death, then a flashback to the love story of a preppy hockey jock, Oliver Barratt IV (David Albury) and Catholic poor person, musician Jenny Cavilleri (Victoria Serra), their ups and downs with their respective parents, a song about pasta, and Jenny's wistful "might have been" before she has children: "I will play nocturnes."

Serra sits at the piano for that one, promising the unborn bairns Bach - and The Beatles, of course - and both the Joplins, Janis and Scott. It's a deft, poignant lyric by Clark, matched by the sparse lyricism of Goodall's music.

There is much to relish in the show, there always was (it opened at the Chichester Minerva four years ago, moving in to the Duchess), in terms of its skill and artistry. But although we are now spared the movie's signature bad line, "love means never having to say you're sorry," it can't help being "so what" sentimental and resistible, especially as the characters are dud and the playing here doesn't enliven them.

My favourite sequence is Goodall's ingenious development and descant on the movie's great schmaltzy theme tune by Francis Lai, taken up in a chorale that I wanted to last quite a bit longer. And instead of Andy Williams singing "Where do I begin?" to tell the story of how great a love can be, we have the more baffled, more interesting "What Can You Say?" ensemble number by the graveside, start and finish.

Regan's staging is perfectly attuned to the space, with a likeable small ensemble, Neil Stewart notable among the parents (he's Jenny's Italian dad), and a nifty quartet (violin, cello, guitar) led by Inga Davis-Rutter on keyboards. The prime pleasure, as always at the Union, is to hear good stuff well sung and played "in the raw" with no vocal amplification. I'm only sorry that, much as I admire it, I still can't write a love song to Love Story.

Love Story continues until 25 October 2014