A book came up on hackernews called Janet for Mortals, it's a book about a language called Janet which is a lisp. The book itself looks great but the key thing to note is the damn repl.
The author added a repl directly to the page and I just love the idea of it and how it fits with everything. There is a bottom bar on the page that activates when you press the escape key. You can now type janet code as you read and see the results. Very frikken cool.
I don't know if I like it more or less than the idea of keeping a terminal window open right next to the text and learning that way. But this is also a very cool way of integrating the repl.
I want to implement something like this for BASIC. That would be fun!