I maintain a programming language called Ferret [1]. You can read through the manual, it is a literate program, covers everything you need to implement your own lisp. Compiler, optimizations, runtime, garbage collection etc. [2] overlaps with [1] covers how to compile a restricted subset of Clojure to C++. If you are interested in interpreters [3] has an implementation of the "A Micro-Manual for Lisp - not the whole Truth" in C.