For this book, you need to download and set up Android Studio and the latest SDKs. Android Studio is free and is available for Windows, OSX, and Linux.
Having at least one phone, phablet, or tablet is strongly recommended, but in Chapter 1, Welcome to Android Studio we will introduce you to Genymotion, a really fast emulator, which you can use instead of a real device in most cases.
Finally, for some recipes, you need to have a Google developer account. If you do not have one yet, I suggest that you get one as soon as possible. After all, you will need one in order to be able to get your app into the Play Store.