This (and several other syntactic / stylistic quirks) made vastly more sense after I learned Prolog, FWIW. Erlang was originally implemented in Prolog, by someo

This (and several other syntactic / stylistic quirks) made vastly more sense after I learned Prolog, FWIW. Erlang was originally implemented in Prolog, by someone who wanted to make a variant of Prolog with better support for concurrency, so it's not surprising that Erlang inherited several of its surface details. As introductions go, _The Art of Prolog_ is also a great book (like SICP great), and spends a lot of time on the logic programming paradigm and its big ideas rather than Prolog-specific details. _Clause and Effect_ by Clocksin is a _The Little Schemer_-like intro, though its style is a little more conventional.