I think that the title is meant to be interpreted as "(A Gentle Introduction to Monad Transformers) – or, (Values as Exceptions)" rather than "(A Gentle Introdu

I think that the title is meant to be interpreted as "(A Gentle Introduction to Monad Transformers) – or, (Values as Exceptions)" rather than "(A Gentle Introduction to ((Monad Transformers) – or, (Values as Exceptions)))". That is, I think that the intention is to introduce the reader to monad transformers by reifying exceptions into values (and thus arriving at monad transformers), rather than to give the reader a complete understanding of monad transformers, which are (in this hypothetical world) the same thing as exception-reifying values.