Both my books pay central attention to demystifying interfaces in functional languages. As the discussions with Haskell people have shown, this notion and its importance are not clear to many, and there are too many myths about this topic.
And yet all the Haskellers associated with the sponsors listed here:
https://haskell.foundation/donations
along with the Haskellers here:
seem to have been doing rather nicely, despite this alleged lack of clarity regarding the notion of the interface and its importance in programming (functional or otherwise)…