The Little Book of Semaphores
The author Alan B. Downey has released quite a few free books:<p>Check out <a href="http://www.greenteapress.com/" rel="nofollow">http://www.greenteapress.com/</a> including:<p><i>Think Python</i> : <a href="http://www.greenteapress.com/thinkpython/thinkpython.html" rel="nofollow">http://www.greenteapress.com/thinkpython/thinkpython.html</a><p><i>Think Bayes</i> : <a href="http://www.greenteapress.com/thinkbayes/index.html" rel="nofollow">http://www.greenteapress.com/thinkbayes/index.html</a><p><i>Think Complexity</i> : <a href="http://www.greenteapress.com/complexity/index.html" rel="nofollow">http://www.greenteapress.com/complexity/index.html</a><p><i>Think Stats</i> : <a href="http://www.greenteapress.com/thinkstats/index.html" rel="nofollow">http://www.greenteapress.com/thinkstats/index.html</a>