The experience of reading a book in a single sitting is qualitatively different from reading it over days or weeks. The world the book creates is more immersive because you haven't left it. The pacing the author intended is preserved. The connections between early and late sections are accessible because you haven't forgotten the early ones.

I try to read novellas in single sittings whenever possible. The form is calibrated for that kind of reading — Conrad's Heart of Darkness, Kafka's The Metamorphosis, Penelope Fitzgerald's The Bookshop. These are books that are damaged by interruption.

Long novels resist single-sitting reading for obvious reasons, but there's a middle-length novel — 200 to 280 pages — that I think benefits from being read in two long sessions rather than spread across two weeks. The concentration matters.