Critic Dave Thompson in Allmusic wrote: "['So in Love' is] a rich and sumptuous number, virtually a ballad, but its adamant beats, swelling synths, and dense textures were all well in keeping with the group's signature styling. The music is swept in warm romance, but counterintuitively the lyrics are as cold as ice, as Andy McCluskey passionately declares an end to love." Colleague Tom Schulte described "So in Love" as being – along with the following year's "If You Leave" – the "pinnacle" of the band's musical progression.
Although "So in Love" was the first single from Crush, it was one of the last songs written for the album. It was originally dropped until band member Martin Cooper persuaded Andy McCluskey and Paul Humphreys to make a demo for the song. Andy McCluskey said it was about the painful end of a relationship. It was their first hit in the United States, after five years of trying to "break" in the States.
The first approximately 50,000 copies of the 7" singles were released as a limited edition double-pack in a gatefold sleeve. There were four different 12" singles released, and one of these was also released as a picture disc. The first issue had the normal version of the song on the A-side, with an extended version of "Concrete Hands" on the B-side. Later issues included remixes of "So in Love" on the A-sides. Three remixes were made, the "Extended Version", "New Extended Version", and "Brand New Extended Version", also known as the "Special American Dance Remix".
"Concrete Hands" was released on the B-side of the 7" singles, and an extended version on the B-side of the 12" singles. It was also released on the Navigation: The OMD B-Sides compilation album in 2001. The lyrics were made of lines written on postcards sent by Andy McCluskey to his girlfriend. "Maria Gallante" was an extra song on the 12" releases and can also be found on the second disc of the 7" double pack. Until now, it is not available on CD. The song takes its title from the Caribbean island Marie-Galante, although the lyrics deal with a girl. "White Trash" is a song from the album Junk Culture. This live recording was recorded at Hammersmith Odeon on 3 October 1984, and was only released on the double 7".