Epistolary novel is a novel told entirely through letters, diary entries, or other documents.
The epistolary form reached its peak with Samuel Richardson's 'Pamela' (1740) and 'Clarissa' (1748) — vast novels in which characters write hundreds of letters and the reader watches a moral crisis unfold in real time. The technique borrows the intimacy of a private document: we eavesdrop. Laclos's 'Les Liaisons Dangereuses' (1782) weaponised it for seduction and revenge; Mary Shelley's 'Frankenstein' (1818) framed her gothic tragedy in nested letters. The form has been continuously reinvented — Bram Stoker's 'Dracula' uses telegrams and newspaper clippings, and contemporary novels assemble emails, texts, and chat logs. The epistolary novel persists because it solves a hard problem: how to show a mind in motion without an omniscient narrator getting in the way.