1. A method comprising: relating, using at least one computing system, each content item in a plurality of content items with a plurality of content item topics, each content item having a plurality of relevance values corresponding to the plurality of content item topics, each relevance value reflecting a strength of relationship between a topic of the plurality of content item topics and the content item; identifying, using the at least one computing system, topics of interest to a user, the topics of interest being identified for the user from a content item browsing history of the user, each identified topic of interest corresponding to a topic of the plurality of content item topics and having a level of interest that exceeds a predefined user-interest threshold; 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 the set of content items, each content item in the set having a relevance determined using the strength of relationship between the topic of the plurality of content item topics and the content item; and ranking, using the at least one computing system, the set of content items based on the determined relevance of each content item in the set.