<em>Since you've been gone</em> is the subordinate clause.
The word since is a subordinate conjunction, and the rest of it is the subject (you) and been gone is a very phrase for the subordinate clause.
you've been gone explained above.
finished the book is the predicate of the main clause. finished is a verb and the book is the object.
practical
Even though Grendel seems as though he's being harsh by eating the exile, he is actually being practical. He says he tries to do things that are more considerate like befriending or ignoring him. However, since the exiles were treacherous, eating them is the most practical solution.
