that if the filmmakers just follow the books 
(ROOT (SBAR (IN that) (IN if) (S (NP (DT the) (NNS filmmakers)) (ADVP (RB just)) (VP (VBP follow) (NP (DT the) (NNS books))))))
(ROOT (SBAR (IN ) (IN ) (S (NP (DT ) (NNS )) (ADVP (RB )) (VP (VBP ) (NP (DT ) (NNS ))))))