1. A computer-implemented method for identifying relationships between a plurality of digital text volumes in a corpus, the method comprising: comparing the plurality of digital text volumes in the corpus to produce volume similarity data describing similarities among pairs of digital text volumes; identifying a cluster of similar digital text volumes based on the volume similarity data; comparing pages of a pair of digital text volumes within the cluster to determine page similarity data indicating degrees of similarity between the compared pages; extracting signals from the volume similarity data and the page similarity data that describe a relationship between the pair of digital text volumes, the extracted signals including at least one of: a measure of linear page-to-page fit that models volume text uniformly distributed across pages of the pair of digital text volumes; and a measure of relative consecutive page correlation between pages of the pair of digital text volumes; classifying the relationship between the pair of digital text volumes based on the extracted signals; and storing classification data describing the relationship between the pair of digital text volumes.