How many letters does the top answer for “author of the screwtape letters” have?

The most common answer is lewis (5 letters).

Crossword clue: author of the screwtape letters

1 answer found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

lewis 5 letters wd-fact-v3

English critic and novelist; author of theological works and of books for children (1898-1963)

author of the purloined letter 50% similar → poe

author of the scarlet letter 50% similar → hawthorne, moore

wrote the screwtape letters 50% similar → lewis