You can find a great introduction to Data Science in Introduction to Data Science, a very interesting Coursera course. The instructor is Bill Howe, Director of Research Scalable Data Analytics at the University of Washington. You can find more details from the following location:
https://www.coursera.org/course/datasci
The course has a very interesting section about Machine Learning. In this section, you will find a very intuitive introduction to entropy, information gain, and Decision Tree Learning.
In the last chapter, we've referenced Machine Learning with R, Brett Lantz, Packt Publishing. In this book, you can find a section about Decision Trees and the author develops an example using the German Credit dataset.
