A lot of his books aren't really fiction but scientific essays that he prepared for publication.
( ( ( A lot ) ( of ( his books ) ) ) ( ( ( are n't ) ( really ( ( fiction ( but ( scientific essays ) ) ) ( that ( he ( prepared ( for publication ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT A) (NN lot)) (PP (IN of) (NP (PRP$ his) (NNS books)))) (VP (VBP are) (RB n't) (VP (ADVP (RB really)) (JJ fiction) (PP (CC but) (NP (JJ scientific) (NNS essays))) (SBAR (IN that) (S (NP (PRP he)) (VP (VBN prepared) (PP (IN for) (NP (NN publication)))))))) (. .)))
He wrote a lot of scientific essays.
( He ( ( wrote ( ( a lot ) ( of ( scientific essays ) ) ) ) . ) )
(ROOT (S (NP (PRP He)) (VP (VBD wrote) (NP (NP (DT a) (NN lot)) (PP (IN of) (NP (JJ scientific) (NNS essays))))) (. .)))