The Little Schemer and The Seasoned Schemer are both beginner books using Scheme. The Reasoned Schemer uses Scheme + Minikanren, an extension of Scheme that allows for logical/relational programming (look up Prolog and Datalog as languages in the same vein). The Little Typer is the linked book covering type systems and, specifically, dependent typing. The Little Learner covers machine learning. The Little Prover uses the same format and has you develop proofs.
Little, Seasoned, and Reasoned are, IMO, the better books in the series to start with. I found the later ones to be good but very dense and not always as clear, had to step back a lot more and reread sections. That's mostly due to the material being much harder and more technical than the earlier books, not a quality issue with the writing itself.
My recommend reading order for someone with no Racket, Scheme, or Lisp experience wanting to tackle the series would be: Little -> Seasoned -> [Optional: Reasoned] -> {Any order: Prover, Typer, Learner}. I think Prover may be better before Typer, but it's been a while since I looked at either, so a soft recommendation of Prover -> Typer.
If you have some Racket, Scheme, or Lisp experience, I'd suggest to either skim the first couple books to get used to the format or skip them entirely and use Reasoned as your first book in the series.
