Merge pull request #1441 from katgironpe/master

Added Raspberry Pi: Measure, Record, Explore

free-programming-books.md

@@ -1611,7 +1611,7 @@ See also [TeX](#tex)
 
 ### Raspberry Pi
 * [Raspberry Pi Users Guide](http://www.cs.unca.edu/~bruce/Fall14/360/RPiUsersGuide.pdf) (PDF) - Eben Upton
-
+* [Raspberry Pi: Measure, Record, Explore](https://leanpub.com/RPiMRE)
 
 ### REBOL
 * [Learn REBOL](http://www.lulu.com/shop/nick-antonaccio/learn-rebol/ebook/product-17383182.html) - Nick Antonaccio