Redis is pretty simple to learn. Install Redis, read the online installation, and play with it from the command line and you will have a good understanding in an hour or two. For many developers the online documentation and samples on the Internet is all they will need to understand and appreciate Redis.
Other developers, however, may struggle with understanding the value of Lists, Sorted Lists, Sets, Hashes, Pub/Sub, and other data structures and functionality in Redis that make it much more useful than a key value store. If you find yourself struggling as to why these additional structures may provide value in your applications and how you can leverage them, I think Redis Cookbook may help bridge this gap and provide you some "aha" moments.
It wasn't until I read the examples in the book that I got a much better appreciation as to how I can leverage the additional data structures in Redis besides a Key Value Store. Quite frankly, I didn't spend that much time looking at the example code ( mostly command line, Node.js, and Ruby ) as I did reading about how to leverage the data structures. The Discussion portion of the problem-solution-discussion formula was actually really good at describing the usefulness of the additional data structures, the API, how to use them and how NOT to use them. I suspect you could find this material all over the Internet, but there is a value to having it packed nice and neatly in the form of a book with good examples.
I received this book for free as part of the O'Reilly Blogger Program, and the question I always ask myself is if I would pay for it with my own money. Based on the description of the book, I would say no. The description really doesn't do the book justice. It focuses on solutions to problems, and really the book does a good job of teaching the fundamentals of using the additional data structures and why/how you use them. After reading the book and appreciating the discussion of fundamentals, I would spend the money on it because it really helped me understand the value of Hashes, Sets, Lists, etc. in Redis for use in my applications.
That being said, the book is really for those struggling to understand the usefulness of the additional data structures and functionality in Redis. If this is a no-brainer for you, save your money as the online documentation and various samples on the Internet will probably serve you fine. If like me, however, you were having a difficult time understanding the value of Hashes, Sets, Lists, etc., the Redis Cookbook will help.