Please, read "The 88 Generalizations about Free Voluntary Reading" by Steven D. Krashen

http://www.sdkrashen.com/handouts/88Generalizations/index.html

Here are some of the most remarkable scientific findings:
More reading means:

better TOEFL performance
(Constantino, S.Y. Lee, K.S. Cho; Gradman and Hanania)
less writing apprehension (S.Y.Lee)
less memory loss
more hobbies
better sleep

Also: eminent people nearly all are voracious readers (Simonton)
More access to books – more reading
Comfort and quiet – more reading
One positive experience can create a reader
more reading takes place if books available (Von Sprecken)
supplementation that makes reading more comprehensible, interesting can help
(Shin, Manning)
more reading takes place if the teacher reads (Von Sprecken, Wheldall and Entwhistle)