I spend the couple of free days reading the book and it definitely worths it. And instead of keeping that experience only for me I decided to write a blog post.
Why you should read the book
Grunt, along with Gulp, is one of the most popular task runners available. There are more then 1600 plugins developed and we are able to automate almost everything. Especially helpful for front-end development, Grunt is a driving force in the modern Web with more then 7000 downloads per day.
Who is this book written for
The book starts with few words about Grunt but surprisingly continues with some practical examples of usage. I found this as a very good direction, because we may see some real use cases before to go into the details. The next chapters introduce the tasks' writing and some advanced techniques. They cover everything, from the installation of the library to testing and Grunt plugins. The book is roughly 120 pages and it is a nice read for your free time.