1. A system for grouping thematically-related clusters into a two-dimensional visual display space, comprising: an extraction module to extract concepts from content of documents stored electronically; a clustering module to select a set of clusters from a multiplicity of clusters each comprising one or more of the concepts; a theme generator to identify a theme in each of the clusters that comprises at least one such concept within the cluster; a spine placement module to form spines of the clusters sharing at least one theme in common; a comparison module to compare the spines and to place only those spines having a theme unique from any other such spine already placed into a visual display space; a candidate anchor cluster module to identify candidate anchor clusters on the placed spines that each comprise at least one open edge; a spine group generator to generate spine groups, comprising: a spine similarity evaluator to evaluate a similarity of at least one of the spines not placed in the visual display space and each of the placed spines and to place the at least one unplaced spine at the open edge of one of the candidate anchor clusters comprised in the placed spine with the closest similarity; and a cluster similarity evaluator to evaluate a similarity of at least one of the clusters not selected and each of the candidate anchor clusters comprised in the placed spines and to place the non-selected cluster proximate to the candidate anchor cluster with the closest similarity; and a display to display the spine groups in the visual display space.