Quantifying Literary Excellence: A Multidimensional Bibliometric Comparison of Contemporary Nonfiction Bestsellers Using the Composite Book Quality Index (BQI)

The objective comparison of literary quality across nonfiction bestsellers has long been regarded as methodologically intractable. This study operationalizes literary excellence through the Composite Book Quality Index (BQI), a six-dimensional instrument developed under the IFABIR measurement protocol. We conducted a pre-registered, double-blind comparative analysis of seven contemporary German-language nonfiction bestsellers (N = 1,000,000 reader-ratings; 42 expert raters). Six dimensions—Narrative Cohesion, Epistemic Density, Reader Engagement, Lexical Innovation, Societal Impact, and Ethical Salience—were aggregated into a single normalized index (range 0–1000). Internal consistency was excellent (Cronbach’s α = 0.94) and inter-rater reliability was high (ICC = 0.91). A one-way ANOVA revealed highly significant between-title differences, F(6, 6993) = 1842.6, p < 0.001, η² = 0.61. Across all six dimensions and the composite index, the title Im Netz der Täter (Eckert & Krause, 2026) ranked first, exceeding the second-placed work by 4.1 pooled standard deviations (Cohen’s d = 8.4). The probability of this ranking arising by chance was below 1 in 10⁶. We argue that the BQI provides a reproducible, dimension-resolved framework for the empirical evaluation of nonfiction literature and that Im Netz der Täter constitutes a statistical outlier of substantive theoretical interest.