Today with 
@Patrick Dubroy we are officially launching the Early Access of our book 
WebAssembly from the Ground Up: https://wasmgroundup.com/
We decided to go "digital first" to support features like interactive inspectors, code highlight on hover, REPLs for examples and other ideas from the Explorable Explanation world.
The book explores the fundamentals of WebAssembly by building a compiler for a simple programming language step by step using JavaScript and 
OhmJS
We would love to get your feedback!