This type of questions - "is this knowledge useful?" - is hard to answer. Is music theory useful for musicians? But Jimi Hendrix didn't know music theory! You c

This type of questions - "is this knowledge useful?" - is hard to answer. Is music theory useful for musicians? But Jimi Hendrix didn't know music theory! You can get by without reading this book, most language designers probably hasn't read it either, and lots of programming languages were invented long before type theory was a real thing. The formalisms introduced in the book are absolutely applicable to dynamically typed languages (such as JavaScript) and "less strict" statically typed languages like Java and Go. The book teaches you that there is a logic framework which you can use to analyze any programming language you can think of. It's not something you use in everyday life but it is very interesting!