Howard Belsey, Kiki's husband, an art historian and college lecturer, hates the works of the 17th century Dutch painter Rembrandt. In fact, he has been working on a book for a long time called "Against Rembrandt." In his college lectures he criticizes Rembrandt and he seems to oppose beauty in art.
Howard's dislike for Rembrandt, which is a symbol of beauty in the context of the book, increases due to the professor Montague Kipps who wrote a positive book about Rembrandt which became an international bestseller. Howard is jealous of Montague.
Kiki is Howard's wife whom he cheated on. What's most striking about Kiki and Rembrandt is that a work of Rembrandt, a painting of his lover Hendrickje, becomes the medium through which Howard sees and appreciates the beauty of his wife. Howard, who had passed up no opportunity to criticize Rembrandt, finally understands the beauty of Rembrandt's work. He also understands his wife and her beauty.
Beauty is a main theme throughout this book. The contradiction of Howard's character is that despite disliking beauty in art, he is attracted to beauty in people. That is why he falls into the error of cheating on his wife. After damaging both his family ties and his career with his behavior, Howard finally discovers beauty and where beauty lies.
Just like Rembrandt's painting of Hendrickje, Kiki is a plain, natural woman. She is not perfect but she is beautiful and the very end of the book describes how Howard finally comes to realize this.