Many critics argue that there is no singular set of defining or essential elements for the novel. However there do seem to be some basic elements that most would agree are necessary for a work to be considered a novel: plot, point of view, setting, theme, and characterization. These elements, although they may be simply defined, offer great scope when put into practice. For example, the theme of a piece may be rather explicit, or, as in the case of many postmodern and contemporary texts, may be so implicit that it appears to create more questions than it does answers. Nevertheless, we as readers search for theme while reading and assume that it is one of the essential components of the work. The attached essay explores some of the history of the novel which may be helpful for examining the posed question.
Novel is perhaps the most diverse of literary genres and it is impossible to generalize as that would lead to homogenization. It was born with the rise of the middle classes in the 18th century with the likes of Richrdson, Fielding etc. The genesis had steeped it into the Enlightenment logic and rationality. However, a subversion was always already there in the form of a Swift and a Sterne. The linear and rationalistic modernity of the novel had its day and social realism ruled in it. The Romantic period saw the development of the Gothic novel and the Victorian period brought back the sprawling social narratives.
With Modernism, in Woolf, Conrad, Lawrence, the psychical impulse was foregrounded. Joyce experimented with the stream of consciousness novel . With the late-modernists and the postmodernists, the literary avant-garde showed a general propensity towards deconstructing the linear narrative logic so much so that a kind of anti-novel was born through Burroughs, Beckett and the French New Novelists like Grillet who decared that the modernist psychological novel was dead and a new poststructuralist novel of surfaces, leaving out symbolism was born.