too often , the viewer is left puzzled by the mechanics of the delivery 
(ROOT (S (ADVP (RB too) (RB often)) (, ,) (NP (DT the) (NN viewer)) (VP (VBZ is) (VP (VBN left) (S (ADJP (VBN puzzled) (PP (IN by) (NP (NP (DT the) (NN mechanics)) (PP (IN of) (NP (DT the) (NN delivery)))))))))))
(ROOT (S (ADVP (RB ) (RB )) (, ) (NP (DT ) (NN )) (VP (VBZ ) (VP (VBN ) (S (ADJP (VBN ) (PP (IN ) (NP (NP (DT ) (NN )) (PP (IN ) (NP (DT ) (NN )))))))))))