18. The electronic device of claim 16 , wherein the user interface is configured to display a graphic as an indicator of the determined similarity relationship in an area adjacent to the display area for each determined text subgroup linked to the text cluster.
16. An electronic device comprising: a hardware processor; an electronic document manager configured to: determine text subgroups within an electronic text; determine a relevance score for each word of one or more words within the determined text subgroups, the relevance score based on one of a frequency of occurrence of the word within one of the determined text subgroups and a type of the word within one of the determined text subgroups; select, based on input received from a user, a text subgroup from the determined text subgroups that corresponds to a current user position within the electronic text; select, a text seed from the selected text subgroup based on the relevance scores of the words within the selected text subgroup; determine a first similarity relationship between the selected text seed and one or more determined text subgroups adjacent to the selected text subgroup that do not include the selected text seed; create a text cluster corresponding to the current user position by associating the selected text seed with the one or more adjacent determined text subgroups based on the determined first similarity relationship to the selected text seed; determine an activity indication of times when a user has read other determined text subgroups within the electronic text; determining a second similarity relationship between the text cluster and other determined text subgroups link the text cluster to at least one of the determined text subgroups based on the determined second similarity relationship between the text cluster and the other determined text subgroups; and a user interface configured to: display in a first display area, a portion of the electronic text corresponding to the text cluster; and display in a second display area, at least one of the determined text subgroups linked to the text cluster based on the times when the user read the other determined text subgroups.