I've got Harper's Practical Foundations for Programming Languages and it's a great book—he writes clearly and succinctly.
Knowing the lambda calculus helped me one time when I was working as a software engineer: I had just added functions to a little DSL interpreter that was going to make it easy to customize behavior of our product to different customers. (It wasn't ever going to be used by customers directly; it was primarily a tool for the internal team.) It was at this point that I realized we needed some kind of execution time-out: since we could encode functions, we could write down e.g. the Y combinator or the omega combinator and we could get non-terminating programs in this DSL.
Now I work as a programming languages researcher, so the lambda calculus has direct application to my day job.
Those curious might be interested in ISWIM, [1,2] which is an extension of the lambda calculus with an arbitrary set of operators. Like the lambda calculus, this is an abstract language. However, you can add numbers and other operators, and ISWIM-like languages are often used to illustrate new ideas in programming languages.
Syntax is incidental. Boil the syntax away from languages and reduce them to their distilled semantics to get out the essential differences—this is the kind of thing that the lambda calculus makes easy.
I highly recommend reading Landin's The Next 700 Programming Languages [2] as it is a great, short, clear read.
If you read just the first page of the linked paper and work through a few examples, you will likely already know enough about it to read the book. It's really just like equational reasoning in mathematics.
Knowing the lambda calculus helped me one time when I was working as a software engineer: I had just added functions to a little DSL interpreter that was going to make it easy to customize behavior of our product to different customers. (It wasn't ever going to be used by customers directly; it was primarily a tool for the internal team.) It was at this point that I realized we needed some kind of execution time-out: since we could encode functions, we could write down e.g. the Y combinator or the omega combinator and we could get non-terminating programs in this DSL.
Now I work as a programming languages researcher, so the lambda calculus has direct application to my day job.
Those curious might be interested in ISWIM, [1,2] which is an extension of the lambda calculus with an arbitrary set of operators. Like the lambda calculus, this is an abstract language. However, you can add numbers and other operators, and ISWIM-like languages are often used to illustrate new ideas in programming languages.
Syntax is incidental. Boil the syntax away from languages and reduce them to their distilled semantics to get out the essential differences—this is the kind of thing that the lambda calculus makes easy.
I highly recommend reading Landin's The Next 700 Programming Languages [2] as it is a great, short, clear read.
[1]: https://en.wikipedia.org/wiki/ISWIM [2]: https://www.cs.cmu.edu/~crary/819-f09/Landin66.pdf