Structure and Intepretation of Computer Programs vs An Introduction to Functional Programming Through Lambda Calculus

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

Lambda calculus can be done with paper and pencil, but any programming language with lambda (like Python) can work with it.

Learn how to build a functional programming language from first principles.

This book doesn't assume any kind of math or programming knowledge beyond elementary school.