Update README.md

Author: rossant

README.md

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 IPython Cookbook
 ================
 
-This repository contains the recipes of the [IPython Cookbook](http://ipython-books.github.io), the definitive guide to **high-performance scientific computing** and **data science** in Python, by [Dr. Cyrille Rossant](http://cyrille.rossant.net), Packt Publishing, 450 pages, September 2014.
+This repository contains the recipes of the [IPython Cookbook](http://ipython-books.github.io), the definitive guide to **high-performance scientific computing** and **data science** in Python, by [Dr. Cyrille Rossant](http://cyrille.rossant.net), Packt Publishing, 500 pages, September 2014.
 
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