Text talks about matching constructor pattern UnOp("-", e), with "... and
whose second argument matches e". Since e is being introduced here, it
seems misleading to talk of any argument matching e (as if this could
fail.) It'd be better to state something like that anything at that
position in the expression is considered a match, and e is bound to that
part of the expression.

FIXED in 4th printing

The text mentions "the react example given above".  However, there is no
"react example".  I'm guessing you mean to say "receive example" or "Akka
actor example".

FIXED in 3ed 4th printing.