1. A document reading apparatus presenting a plurality of documents designated as reading documents by a user, comprising: a thematic hierarchy recognizing device recognizing a thematic hierarchy of each of the plurality of documents; a topic extracting device extracting a topic that commonly appears in the plurality of documents based on the recognized thematic hierarchies; and a topic relation presenting device taking out a description part corresponding to the extracted topic from each of the plurality of documents and outputting the taken-out description parts.