I feel that all talks by Jon Ingold, show the peak of the medium. So he could benefit from that wisdom by looking for them on youtube and seeing them in chronological order. (little by little, because the philosophy of them builds and builds upon the previous Jon’s experience through the years… so maybe your friend wants to consume them little by little).
I’ve created a list on youtube:
Also, I would recommend this first GDC for Jon Ingold at GDV Vault (for free):
Also, I would recommend reading some classics, like The craft of adventure, by Graham Nelson. and Crimes against mimesis, by Roger Giner-Sorolla. Those are a good start to Interactive Fiction authoring with game world and parser.
For choice-based IF, the top-notch design is the philosophy of Choice of Games: “Delayed branching”, that you can learn about here:
Lastltly, Standard Patterns in Choice-Based Games, by Sam Kabo Aswell, a modern seminal:
That’s it for now!