I disagree with recommendation of Lua. Lua is a production-grade interpreter, and a production-grade interpreter is usually not a good educational material for

I disagree with recommendation of Lua. Lua is a production-grade interpreter, and a production-grade interpreter is usually not a good educational material for those "interested in interpreters". In particular, Lua uses no intermediate representation (there is no Lua AST!), which makes its compiler portion a quite confusing read. Its interpreter portion is no less confusing, being a register VM with a register window scheme and a non-recursive eval using goto and a separate call stack. Do not be fooled by "not too large" aspect. Lua is worth studying, but it is definitely not a beginner material.