Neural Networks and Deep Learning By Michael Nielsen

http://neuralnetworksanddeeplearning.com/index.html

Neural Networks and Deep Learning is a free online book. Thebook will teach you about:

Neural networks, a beautiful biologically-inspired programmingparadigm which enables a computer to learn from observational data
Deep learning, a powerful set of techniques for learning in neuralnetworks

Neural networks and deep learning currently provide the best solutionsto many problems in image recognition, speech recognition, and naturallanguage processing. This book will teach you many of the coreconcepts behind neural networks and deep learning.
For more details about the approach taken in thebook,
see here. Or you can jump directlyto
Chapter 1 and get started.