Structure and Intepretation of Computer Programs vs Coursera - "Compilers" by Stanford

This isn't a book you'll glean direct practical tidbits out of, an introduction to not only functional programming but how to think in a paradigm outside the usual way C*/Python/Ruby/Java/etc... are coded.

Even if you wind up never working in Scheme or any other primarily functional language, the tactics and thought processes you'll learn here will apply to any currently-evolving language to a greater or lesser degree. You'll be able to map your thought process into the paradigm that works best for your current situation and not just be forced into a limited set of idioms that causes unnecessary boilerplate and clunky code mangling.

Like closures and encapsulation without language support of objects.

This book gives a great insight about immutable and mutable state (with pros and cons), typisation, FP, OOP, and many other things in a very beginner-friendly manner

When the course is run, it is taken by thousands of students world-wide. Coursera provides a forum where you can discuss the material with others.

There is no cost to take this course.

After successful completion of the course, the student will receive a statement of accomplishment.