unrelentingly grim -- and equally engrossing 
(ROOT (ADJP (ADJP (RB unrelentingly) (JJ grim)) (, --) (CC and) (ADJP (RB equally) (JJ engrossing))))
(ROOT (ADJP (ADJP (RB ) (JJ )) (, ) (CC ) (ADJP (RB ) (JJ ))))