Book by Eric Normand (a Clojure developer) written with JavaScript examples, teaching functional programming through the lens of three categories — data, calculations, and actions — plus stratified design and visualization techniques (call graphs, timeline diagrams). Wójtowicz bases his wroclove.rb 2022 'Grokking FP For The Practicing Rubyist' talk on this book and recommends it as the long-form version, noting that the ideas are language-agnostic and equally applicable to Ruby despite the JavaScript examples.