Below are some of the Scratch Books that I recommend. There are many other Scratch books available, but these are the books that I have read and recommend. I link to the books on Amazon (non-affiliate links), but all the books are available from other retailers.

Learn to Program with Scratch: A Visual Introduction to Programming with Games, Art, Science, and Math by Majed Marji (2014)
I highly recommend this book for anyone new to Scratch and programming in general. It's a true programming book and great for teachers and parents looking for a deeper understanding of computer programming concepts in the context of Scratch. It's full of excellent example projects and visual explanations that really drive home complicated concepts. I consider it the textbook for Scratch.

Chapter 1 starts with a thorough introduction of the Scratch environment. By the time you finish chapter 6, you'll have solid understanding of all the core Scratch blocks and how they connect with programming concepts. The remainder of the book (chapters 7-9) covers more advanced topics, such string processing and lists. The book also has excellent mathematical explanations for many topics, including: graphing, loops, animation and procedural drawing.

Coding Games in Scratch by Jon Woodcock (2015)
This book takes a different approach than Learn to Program with Scratch by walking you through the process of building ten games in Scratch. The book starts with a nice chapter on game design fundamentals then follows with a brief introduction to Scratch. The games increase in difficulty with each chapter and are very fun to play and customize.

Scratch Programming Playground by Al Sweigart (2016)
This wonderful free book by Al Sweigart walks you through the process of building eight games. Each chapter introduces a new game of increasing difficulty and programming concepts are explained along the way. By the end of the book, you'll have a fun collection of games to play and build upon: "Maze Runner", "Fruit Slicer", "Advanced Platformer" and more.