Middlemarch is a novel that falls into the category of realism. This is because it does not romanticize the everyday lives of rural people and pays close attention to politics and setting. In other words, it is a “realistic” depiction of what provincial life was like in England in the early 1830s.
Though Middlemarch certainly focuses on romantic relationships, it is not a “romantic” novel. Unlike Jane Austen, for example, Eliot captures the reality of unhappy marriages rather than closing the novel with a series of engagements or happily ever afters. In fact, the majority of the romantic relationships in Middlemarch result in suffering on both sides, as seen most clearly in the marriages between Casaubon and Dorothea and Rosamund and Lydgate.
Middlemarch is sometimes considered a work of historical fiction because Eliot wrote the novel in the early 1870s and it takes place in the early 1830s. That said, some scholars argue that the passage of 40 years is not enough time to render it a historical novel. One of the reasons “historical fiction” possibly fits the bill, though, is because Eliot was intentionally writing about the period surrounding the 1832 Reform Act in order to reveal truths about the time in which she was writing (just after the passing of the Reform Act of 1867).