In 1972 or 1973 (possibly 1974) I read a hardcover library book that took place almost entirely on Earth, and largely in major U.S. city (probably Manhattan).
This was a light comedy, and is mostly a light, comedic mainstream novel. Not serious. During the story, Mariner 9 begins to orbit Mars, and images the global dust storm on Mars. (Those two events actually happened, which tells me that the novel must have been written AFTER late 1971). A delightful revelation is that unseen Mars-based Martians turned on giant fans to produce the dust storm so as to hide their presence from humanity.
Near the end of the novel a Martian spacecraft lands atop a skyscraper (probably located in the City of New York). On the side of the boxlike spacecraft is the word Fedders. The Martian spacecraft is, of course, disguised as an ordinary, large air-conditioning unit. At the end of the story, perhaps, a man and woman fall in love. They were aware of each other, or, more likely, interacted, throughout the novel.
This novel was probably NOT written by a "name" science fiction author. It was good, and was one of those novels that has one foot solidly in mainstream, light fiction. Fedders is the name of an actual, prominent air conditioning firm.