DELETE query failing in CQL 3.0

[Ryabin, Thomas]

I have a column family called "books", and am trying to delete all rows where 
the "title" column is equal to "hatchet". This is the query I am using:
    DELETE FROM books WHERE title = 'hatchet';

This query is failing with this error:
    Bad Request: PRIMARY KEY part title found in SET part

I am using Cassandra 1.1 and CQL 3.0. What could be the problem?

-Thomas