I know this is a possibly unpopular opinion but I don't think one should glorify a sophomoric book as a key Ruby book-- there are others that deserve that title, PickAxe is close, but I'd have liked a book like Whittaker's "C#, Player Guide" for Ruby.
Matz's intent was and has been to bring joy and delight to developers, with the odd combination of PERL, LISP, and Smalltalk as his inspirations. Joy and delight don't necessarily equate with "most practical". But joy and delight are wonderful and healthful qualities to cultivate for a good life!
_why embodied much of the spirit of the (at least earlier) Ruby community. We were software developer immigrants, many coming from prescriptive verbose technologies (I'm looking at you, Java!). We were eager for novel ways of expressing our ideas. Ruby's metaprogramming capabilities are, as far as I know, still all but unmatched beyond perhaps Smalltalk itself (and IO, which AFAIK no one uses seriously). _why's playfulness captured all of this in elegant and sometimes bizarre but often artistic expressions in his projects and code.
I will never regret or apologize for the Ruby community's appreciation for the Poignant Guide.
And, _why, wherever you are and whoever you are, thanks.