Here you find the four books about Pharo from http://books.pharo.org

- Pharo by Example, intended for both students and developers, will
  guide you gently through the Pharo language and environment by means
  of a series of examples and exercises.

- Deep into Pharo is the second volume of a series of books covering
  Pharo. Whereas the first volume is intended for newcomers, this
  second volume covers deeper topics.

- Enterprise Pharo is the third volume of the series. This book covers
  libraries and frameworks for enterprises, and in particular those
  doing web development.

- Numerical Methods: Mathematics with Pharo