bottle episode
n.— «Even though they are moving, for large stretches “Spiral” is a bottle episode.…They are in the Winnebago, or the gas station, and it is a contained story.» —by Roz Kaveney Reading the Vampire Slayer Mar. 18, 2004. (source: Double-Tongued Dictionary)
Further reading
The rare adjective finifugal describes someone “averse to endings” or “wishing something could go on forever,” whether it’s a book, a beloved TV series, a podcast, or anything else you don’t want to end. It comes from Latin finis, “end,” and fuga...
Paul in Batavia, New York, recommends The Door-to-Door Bookstore (Bookshop|Amazon), a novel by Carston Henn, translated from German by Melody Shaw, which includes a wonderful description of a book with a perfect final paragraph that you nevertheless...