6. The method of claim 1 , wherein determining a rank score for each of the two or more distinct book content items comprises: representing the two or more distinct book content items as a graph in computer memory, where each of the distinct book content items is represented as a distinct node in the graph and where an edge exists in the graph between each pair of distinct nodes that represent distinct book content items that both include a similar image; and determining a rank score for each of the two or more distinct book content items based on the edges between the distinct nodes.
6. The method of claim 1 , wherein determining a rank score for each of the two or more distinct book content items comprises: representing the two or more distinct book content items as a graph in computer memory, where each of the distinct book content items is represented as a distinct node in the graph and where an edge exists in the graph between each pair of distinct nodes that represent distinct book content items that both include a similar image; and determining a rank score for each of the two or more distinct book content items based on the edges between the distinct nodes. 7. The method of claim 6 , wherein the rank score for each distinct node is based on the edges connecting distinct nodes corresponding to distinct book content items that satisfy a search query.