Depending on how involved the language you are interpreting is, you might get by having only read chapter 6 of The AWK Programming Language[0] (linked in the article), which covers "Little Languages", including what it terms an assembler and interpreter.
If you are interested in more depth, either Crafting Interpreters[1] (mentioned in the article) or Writing an Interpreter in Go[2] looks promising. I've read more of Crafting Interpreters and really enjoy it, though it isn't yet finished. One of the aspects I really enjoy is that the language is implemented and re-implemented in different languages to gradually introduce lower level concepts.
Finally, this one may be a little more "out there" than what you are looking for, but if you are interested in designing a language more than the plumbing of an interpreter Beautiful Racket[3] is really good.
caveat: not an expert
[0]: https://ia802309.us.archive.org/25/items/pdfy-MgN0H1joIoDVoI...
[1]: http://www.craftinginterpreters.com/