Claims for Oroonoko's being the "first English novel" are difficult to sustain. In addition to the usual problems of defining the novel as a genre, Aphra Behn had written at least one epistolary novel prior to Oroonoko. The Love-Letters Between a Nobleman and His Sister predates Oroonoko by more than five years. However, Oroonoko is one of the very early novels in English of the particular sort that possesses a linear plot and follows a biographical model. It is a mixture of theatrical drama, reportage, and biography that is easy to recognise as a novel.
Oroonoko is the first English novel to show Black Africans in a sympathetic manner. At the same time, this novel, even more than William Shakespeare's Othello, is as much about the nature of kingship as it is about the nature of race. Oroonoko is a king, and he is a king whether African or European, and the novel's regicide is devastating to the colony. The theatrical nature of the plot follows from Behn's previous experience as a dramatist. The language she uses in Oroonoko is far more straightforward than in her other novels, and she dispenses with a great deal of the emotional content of her earlier works. Further, the novel is unusual in Behn's fictions by having a very clear love story without complications of gender roles.
Critical response to the novel has been coloured by the struggle over the enslavement of black Africans and the struggle for women's equality. In the 18th century, audiences for Southerne's theatrical adaptation and readers of the novel responded to the love triangle in the plot. Oroonoko on the stage was regarded as a great tragedy and a highly romantic and moving story, and on the page as well the tragic love between Oroonoko and Imoinda, and the menace of Byam, captivated audiences. As the British and American disquiet with slavery grew, Oroonoko was increasingly seen as protest to slavery. Wilbur L. Cross wrote, in 1899, that "Oroonoko is the first humanitarian novel in English." He credits Aphra Behn with having opposed slavery and mourns the fact that her novel was written too early to succeed in what he sees as its purpose (Moulton 408). Indeed, Behn was regarded explicitly as a precursor of Harriet Beecher Stowe. In the 20th century, Oroonoko has been viewed as an important marker in the development of the "noble savage" theme, a precursor of Rousseau and a furtherance of Montaigne, as well as a proto-feminist work. Most recently, Oroonoko has been examined in terms of colonialism and experiences of the alien and exotic.
Recently (and sporadically in the 20th century) the novel has been seen in the context of 17th-century politics and 16th-century literature. Janet Todd argues that Behn deeply admired Othello, and identified elements of Othello in the novel. In Behn's longer career, her works center on questions of kingship quite frequently, and Behn herself took a radical philosophical position. Her works question the virtues of noble blood as they assert, repeatedly, the mystical strength of kingship and of great leaders. The character of Oroonoko solves Behn's questions by being a natural king and a natural leader, a man who is anointed and personally strong, and he is poised against nobles who have birth but no actual strength.