Fiction writers are rightly advised to use said in dialogue and avoid redundancies or conspicuous synonyms: ‘You must,’ he insisted. ‘The hell I will!’ she shouted loudly. This sort of thing is likely to annoy readers and distract them from the story. It’s one of Elmore Leonard’s 10 rules of writing:
Never use a verb other than “said” to carry dialogue. The line of dialogue belongs to the character; the verb is the writer sticking his nose in. But “said” is far less intrusive than “grumbled”, “gasped”, “cautioned”, “lied”. I once noticed Mary McCarthy ending a line of dialogue with “she asseverated” and had to stop reading and go to the dictionary.
Yet writers continue to riddle their stories with showy or gratuitous synonyms. It can give the impression that they’re trying too hard to enliven their text, without knowing the right and wrong ways to translate their passion for the material into something readers will appreciate, not wince at. If you’re going to thesaurify said, you’ll need a damn good reason.
Horror writer Ramsey Campbell had a good reason in his short story ‘Next Time You’ll Know Me’ (1988), which plays around with the ownership of ideas and the challenge of being original. Its narrator deliberately overwrites his account, studiously avoiding said in almost every report of speech in favour of overblown alternatives: