1. A method comprising: relating, using at least one computing system, each content item in a plurality of content items with a plurality of topics, each content item being related to each topic by a relevance value reflecting a strength of relationship between the topic and the content item; identifying, using the at least one computing system, topics of interest to a user, the topics of interest being identified from a content item browsing history of the user; identifying, using the at least one computing system, a set of content items as recommendations for the user by iterating through the topics of interest to the user to identify a set of content items, each content item in the set having a relevance determined using the strength of relationship between the topic and the content item; and ranking, using the at least one computing system, the set of content items based on the relevance of each content item in the set.