I found the book "An Introduction to Lambda Calculi for Computer Scientists"[1] to be a good intro to these concepts. For those who want to go further, books by Henk Barendregt[2] are widely considered to be a reference to lambda-calculus and combinators.

Fresh out of college I was really into lambda calculus and combinators, and wrote a pretty similar blog post to this article, maybe just a bit simpler: https://log.kv.io/post/2008/03/02/ski-calculus-in-haskell-sh...

[1] https://www.amazon.com/dp/0954300653

[2] "The Lambda Calculus — Its Syntax and Semantics" and "Lambda Calculus with Types"