Search is not ready yet. If you need to use search now please use older version of the site.
Plan is to make very powerful search page with query builder and faceted search.
Faceted search will allow you to easy narrow down results by different criteria (e.g. content type, author, category/topic, book hierarchy)
With Query Builder anybody will be able to make elaborate queries using features like boolean operators, choosing which fields to search, choosing whether to use stemming, etc.