Although the lambda papers talk about Scheme, that's not what they're really about. They're really about... lambda. The takeaway is that many common features of languages can be thought of as disguised uses of the lambda operator. So lambda is actually the unifying abstraction behind many languages, even if they don't know it.

The original 'Lambda the Ultimate X' papers are very short, so no reason not to give them a try.

Scheme is just the language used to give concrete examples for a set of papers about Lambda.

Guy Steele is one of the greatest communicators in computer science. Brilliant and charming.

Check out as much of his stuff as you can, like Growing a Language (on YouTube and in print).