Shopgirl is a novella written by Steve Martin. It is around 120 pages, which makes it either a longer novella or a shorter novel. It was published in 2000, and could be considered "literary fiction", that is, it is not of a particular genre, but is a realistic tale in subject matter and style.
The book is a hesitant love story, between the titular shopgirl, her slacker admirer, and a wealthy older business man. As mentioned in the above review, the story is minimalist in both its topic and its presentation. There is a young woman of the 1990s, with a fairly typical background and attitude, who is having fairly typical romantic problems. Although one of her admirers is a wealthy older man, it is a fairly believable situation.
That being said, the fact that this is an understated work of modern fiction is more remarkable given who its author is. When I read a book by a celebrity, one of my first questions is "Would this book be published if the author was not a celebrity". In the case of Shopgirl, the answer is a very strong "yes". Even more strongly, Steve Martin at no point in the book beats the reader over the head with the fact that they are reading a book by Steve Martin. While the lack of humorous prose and subject matter, or absurdist interjections, is obvious, Steve Martin also uses his voice in this book. In fact, he has done what every good author should do: use a distinctive voice, while not beating the reader over the head with it.
This being said, it leads into what I think might be the most important point of the book, and one where Martin's absurdism shows through the serious style of the book. The book is a love story, but one without the usual development, climax or denouement of a love story. The protagonist finds herself in a relationship with an older man, who is more sophisticated than her but perhaps no wiser. In a conventional love story, there would be two ways to play this: either he is Prince Charming, who is going to deliver her from all hardship, or he is a lecherous, manipulative older man. Instead, he is neither. He genuinely loves her, but that love doesn't have the conclusion that either the characters or the audience has come to expect. The book is then, with no pyrotechnics, an absurd love story, a story about love that leaves the reader unsure of what has happened-- which is both absurd and very natural.
There is also other strands to the story, surprisingly many in such a short work. There are many other comments that could be made about the political and social background of the work, but that would perhaps involve too many digressions.
In any case, "Shopgirl" is a serious, thoughtful work of fiction by a man who chose not to coast on his fame.