I think doing a full-text search would definitely be an interesting and challenging exercise. I recommend Solr (but I am committer and am biased :-) ). If they do choose to do that, I would strongly recommend they do it very much in the open with Github repos for schemas and blog writings about the approach chosen.
On a similar project idea, I would love a cross-book character/place cross-referencing. So, if a particular real or imagined character is mentioned in different books, it could be fun to recommend/graph other books related to that. E.g. Moscow, Casanova, etc.
Regards,
Alex.