I see why you might link to the page you did since it has some additional information, and even provides a link to the more recent edition, but be aware that this is an old version of PLAI that has been updated as recently as 2012 [0].
Furthermore, the cs173 class at Brown now uses a different book, Programming and Programming Languages [1], that was updated as recently as 2014. It's very much in the same spirit, but uses Pyret instead of plai-typed.
Another thing to note is that cs173 had a MOOC-like online offering in 2012, and the videos are still available [2].
Thanks for mentioning Pyret, I've searched for it and it made me laugh discovering the extension of the files is .arr (some would say I'm really easily amused).
I've been watching the videos from 2012, and the professor sprinkles that humor throughout the lectures, and done well in that its not annoying (to me at least).
Furthermore, the cs173 class at Brown now uses a different book, Programming and Programming Languages [1], that was updated as recently as 2014. It's very much in the same spirit, but uses Pyret instead of plai-typed.
Another thing to note is that cs173 had a MOOC-like online offering in 2012, and the videos are still available [2].
[0] http://cs.brown.edu/courses/cs173/2012/book/
[1] http://papl.cs.brown.edu/2014/
[2] http://cs.brown.edu/courses/cs173/2012/