<blockquote>The new research, carried out at Emory University in the US, found that reading a good book may cause heightened connectivity in the brain and neurological changes that persist in a similar way to muscle memory.</blockquote>
via <a href="http://www.independent.co.uk/news/science/brain-function-boosted-for-days-after-reading-a-novel-9028302.html">Brain function 'boosted for days after reading a novel' - Science - News - The Independent</a>.

Not very large sample size however...
<blockquote>21 students took part in the study, with all participants reading the same book -  <em>Pompeii</em>, a 2003 thriller by Robert Harris, which was chosen for its page turning plot.</blockquote>