proves unrelentingly grim -- and equally engrossing 
(ROOT (S (VP (VBZ proves) (S (ADJP (ADJP (RB unrelentingly) (JJ grim)) (, --) (CC and) (ADJP (RB equally) (JJ engrossing)))))))
(ROOT (S (VP (VBZ ) (S (ADJP (ADJP (RB ) (JJ )) (, ) (CC ) (ADJP (RB ) (JJ )))))))