How much do readers actually write about whodunit? Tropesmith reads Goodreads reviews, Amazon reviews, BookTok comments and captions, Reddit posts and Amazon Q&A, picks out the specific things readers asked for or praised, and tags each one to the tropes it mentions. Here's the count for whodunit, then the other side: what makes readers walk away.
Counted 2026-10-21 02:40 UTC. A demand signal is one specific thing a reader asked for or praised in a review, comment or post, picked out by Tropesmith's classifier. One review can give several. A signal "mentions" a trope when it is one of the signal's main or secondary tags. Each signal gets a rarity tag (common, underserved or novel) from the text of that review or post alone; the classifier is never shown what is on the shelf. A tag points at where to look. It does not prove that no book answers the signal. Shares are the tagged signals divided by all signals in the same scope. How we count.
Whodunit is the classic-form mystery promise: a closed set of suspects, a fair-play puzzle, and a solution the reader could theoretically have reached first if they'd paid close enough attention. It's the structural backbone the rest of mystery riffs on — cozy softens it, thriller speeds it up, noir darkens it — but the pure form still has its own dedicated audience.
32,919 demand signals mention it, 24% tagged underserved or novel, and 107 titles in Tropesmith's registry of trope-tagged books carry it. The useful question is less "is anyone writing this" and more which setting, sleuth archetype or era is already crowded, which the registry count cannot answer: check comp titles in your sub-niche.
As of 21 October 2026. The registry holds the books Tropesmith has tagged trope by trope and is deepest in romance, so this is a count of tagged titles, not of every book on the shelf.
Demand tells you what readers want written. Rejection tells you how they'll punish it if you get the execution wrong. Tropesmith mines 1–2★ Goodreads reviews for the specific reason a reader gave up, then classifies it against a fixed list of dealbreaker patterns:
Read the numbers together, not separately. 32,919 demand signals tell you how often readers mention whodunit in the reviews, comments and posts Tropesmith has read; 24% tagged underserved or novel tells you how often the classifier tagged those mentions underserved or novel; the registry count tells you how many books Tropesmith has tagged with it. None of them says whether a book that delivers the trope will sell, and none shows what is on the whole shelf. A high tagged share is a prompt to check comp titles for the specific angles readers name; a low one means the classifier tagged fewer of the mentions that way. Pair any of it with the rejection data above: readers punish weak execution of a trope they want just as fast as they ignore one they don't. The full methodology page explains each number and what it leaves out.
Tropesmith's index holds 32,919 demand signals that mention whodunit (counted 21 October 2026) — specific things readers asked for or praised in reviews, comments and posts. 24% of them are tagged underserved or novel by Tropesmith's classifier.
107 titles (as of 21 October 2026). The registry holds the books Tropesmith has tagged trope by trope and is deepest in romance, so for mystery read the count as tagging coverage, not as the size of the shelf.
The most-named dealbreaker in low-star mystery reviews is "Slow / dragging pace" (12,125 mentions summed over the genre's lanes, a review can count more than once, a review can count more than once, 61% DNF rate, meaning the share of those mentions in reviews the classifier marked as a DNF); rejection figures were computed 21 October 2026.
A Tropesmith Map scores your exact trope stack against demand and supply data — and shows where to look next.
Build my Map → See a real sample Map first →Part of Tropesmith's romance market intelligence hub and free research tools. Demand figures are a dated count; registry counts were read on 21 October 2026 and rejection figures were computed on 21 October 2026.