See the github repository.
In this book, you will find descriptions of programs that you can compose (write) in ClojureScript. The programs will usually be short, and each one has been designed to provide practice material for a particular ClojureScript programming area. Unlike musical études, these programs have not been designed to be of considerable difficulty, though they may ask you to stretch a bit beyond the immediate material and examples that you find in most ClojureScript books or online references.
These études are not intended to introduce you to individual ClojureScript concepts. That ground is covered quite nicely by ClojureScript Koans, 4Clojure, and ClojureScript Unraveled. Instead, these études take the form of small projects that do something that is (somewhat) useful. They are much along the lines of the programming katas given in chapter 10 of Living Clojure by Carin Meier. If Koans, 4Clojure, and ClojureScript Unraveled ask you to write programs at the level of chemical elements, in this book you are constructing simple molecules.