Fiction Eval leaderboard · model review

Claude Opus 4.8 for fiction writing — blind-judged review

July 2026: 10 fresh genre scenes, three tries each, judged blind against 7 other frontier models by a different AI family.

Where it lands

#1 of 8 — score 1927 (likely 1888–1976), record 150–14–43 across 207 blind matchups. Slop 14.88 per 1,000 words (3rd-cleanest of the field — a separate AI-tell count, not the quality ranking).

#	Model	Score	Record	Slop
1	Claude Opus 4.8	1927 (likely 1888–1976)	150–14–43	14.88
2	Claude Sonnet 4.6	1914 (likely 1874–1961)	146–15–46	18.57
3	Grok 4.3	1856 (likely 1815–1899)	137–28–42	9.43
4	GLM 5.2	1776 (likely 1732–1822)	117–42–42	17.53
5	Gemini 3.1 Pro	1471 (likely 1423–1519)	78–104–13	13.45
6	DeepSeek V3.2	1251 (likely 1201–1302)	52–144–11	23.24
7	Mistral Large	1118 (likely 1054–1167)	35–162–10	17.79
8	Llama 4 Maverick	686 (likely 627–741)	0–206–1	22.92

Judged strengths and weaknesses

Traits where Claude Opus 4.8 scores above the field average: voice, pacing, dialogue, genre convention, avoiding AI tells. Below the field average: none. (Each rated 1–5 by the judge; field average taken across all eight models.)

Sample

LitRPG — “dungeon-core scene” scene; full version on the board.

I am three days old and I am nearly empty. [MANA: 2/60] The number sits in the dark behind what I am learning to call my sight. I spent the rest — fifty-eight points, everything — hardening the west corridor, packing loose earth into stone because loose earth frightened me. I do not know why it frightened me. I am new. Many things frighten me. Rain has been falling above for a day. I feel it in the soil the way a tooth feels cold water, a long ache down through my single room and my single corridor and into the pebble of crystal that is, apparently, me. Then the ache changes. [PROXIMITY ALERT — LIVING ENTITY] [Entity has entered the Threshold.] Something drags itself in from the rain. I watch — I have no eyes, but the dungeon is my eyes — as it collapses just inside the corridor I hardened. Small. Bent. Ribs like the tines of a broken rake pushing at grey-green skin. It shivers. Water runs …

Head-to-heads

vs Claude Sonnet 4.6 · vs Grok 4.3 · vs GLM 5.2 · vs Gemini 3.1 Pro · vs DeepSeek V3.2 · vs Mistral Large · vs Llama 4 Maverick

How it works: every pair of models is judged blind on the same scene, with the passages' order flipped so being shown first can't sway it, by GPT-5.4 — a family that isn't on the board, so nobody scores their own side. Each score carries a likely range; overlapping ranges are called a tie. Slop is scored separately by a fixed checklist, not an AI. Full board, every prompt, and the FAQ: thebookfactoryai.com/board. Get each new board by email on the model-drop list.

Writing a book of your own? Book Factory runs the same craft checks on full manuscripts.