What is the purpose of Ishiguro's novel The Remains of the Day, especially in relation to Stevens the butler?

The overarching purpose of Ishiguro's novel is to document and describe the decline of the traditional English lifestyle, and he pays particular attention to the rapid changes that took place within the country's traditional class structure during the first half of the Twentieth Century. Stevens is particularly important in the novel because he represents a key component of the old, upper class establishment: the butler. As a butler, Stevens' entire existence relies upon serving his master and the gentry as a whole. In the process of this service, Stevens neglects all of his personal desires, subordinating them to the demands of his job and the needs of the wealthy. By the end of the novel, however, the old upper class has begun to fade away while the middle class rises to prominence, and so it's suggested that Stevens' sacrifice has been unnecessary. All in all, the main point of the novel is to not only describe a changing English class structure, but to also chronicle how this monumental change affects the individuals, such as Stevens, who have given their lives to the established order.