Hello Uberto,
We agree : We can say that referential transparency describes the purity aspect of functional programming. But IMHO, for an ‘Object’ developer it is I think easier to introduce FP via the Side Effects.
In any case, I think it would be good to introduce this notion more concretely via an example or a small code defactoring… So we could see the RT benefits !
In general, the approach proposed in the book based on business tests (and hand in hand) is very interesting. I therefore recommend this book for the object developer wishing to discover the benefits of the functional approach.
Regards,
Philippe