Twenty shelves measured. This is the only one with no publisher on it at all.

Who holds page one

What the numbers say

• An absent incumbent is worth more than a small field. Spot-the-difference has half the competitors and is closed; this shelf has no gatekeeper at all.
• Review counts are tiny — 7, 9, 13, 18 on four of the seven listings. You are not fighting a review moat here, you are joining a shelf where nobody has one.
• The format is standardised at 142–214 pages with 500–650 puzzles. That is a volume promise, and it is the number buyers compare.
• Production is nearly free. A cryptogram is a quote with letters substituted — no illustration, no layout craft beyond legibility. Of every shelf we measured, this has the lowest cost per page.
• The hook is the quotes, not the puzzle. “Funny”, “humorous”, “interesting facts” — the differentiator is what people read while solving, and that is a choice you make in an afternoon.

What I would actually do

Where these numbers come from, and what they are not

Every figure was read off Amazon.com on 18 September 2026: the organic results for that query with sponsored slots removed, then each listing's own page for rank, review count, publication date and length. Prices are US list prices at that moment and move constantly. Best Sellers Rank is a live position, not a sales figure — a rank read on a Tuesday can differ from the same rank on Sunday. “Indie” means the listing shows no traditional publisher, the closest public signal for a self-published title; it will occasionally mislabel a small press. Only paperbacks were counted. And know the width of the lens: this is the first page of one query — eight organic listings — not a census of the niche. A shelf that looks closed to newcomers here may be open on a neighbouring phrase, and seasonality is not accounted for: gift-driven categories rank differently in September than in November. One snapshot is not a trend.