I'm reading another book. It's called Programming Elixir >= 1.6 [https://pragprog.com/titles/elixir16/programming-elixir-1-6/] and it puts the fun in functional. Throughout this book, there're several exercises to deepen the reader's knowledge. And, of course, there's a PDF with solutions [http://media.pragprog.com/titles/elixir16/Elixir_1.