What you need for this book
All you need is a copy of Unity 5.x, which can be downloaded for free from http://www.unity3d.com.
If you wish to create your own image files for the recipes in Chapter 4, Creating Maps and Materials, you will also need an image editor, such as Adobe Photoshop, which can be found at http://www.photoshop.com, or GIMP, which is free and can be found at http://www.gimp.org.