While the latter plot is a fairy tale with many nonsense elements and poems, similar to Carroll's Alice books, the story set in Victorian Britain is a social novel, with its characters discussing various concepts and aspects of religion, society, philosophy and morality.

[3][4] There are two strands to the plot: the conspiracy against the Warden of Outland, instigated by the Sub-Warden and Chancellor, and the love of a young doctor, Arthur, for Lady Muriel.

"[13] In 2014, Mari Ness wrote "Carroll abruptly shifts from one world to the other often without sense or reason or letting the reader know what’s going on.

Other bits leap from here to there without much meaning or connection or recollection of what happened earlier [...] Carroll later noted that he wrote the rest of the book in odd moments here and there, more or less jotting them down when he thought of scenes.

Ness does praise some aspects, such as the Professor's Lecture, and says that "here and there I can catch glimpses of the zany, surreal humor of the Alice books.

[14] Writing in The Forward in 2015, Benjamin Ivry criticised what he saw as antisemitic content in Sylvie and Bruno, for example, the depiction of a tailor (a stereotypically Jewish occupation in Victorian England) who accepts the doubling of his payment owed every year.