This book assumes that you have a reasonably modern desktop or laptop computer as well as a working Clojure environment with Leiningen (see http://leiningen.org/) properly configured. Installation instructions depend on your platform and can be found on the Leiningen website (see http://leiningen.org/#install).
You are free to use any text editor of your choice, but popular choices include Eclipse (see https://eclipse.org/downloads/) with the Counterclockwise plugin (see https://github.com/laurentpetit/ccw), IntelliJ (https://www.jetbrains.com/idea/) with the Cursive plugin (see https://cursiveclojure.com/), Light Table (see http://lighttable.com/), Emacs, and Vim.