Agree! I bought my kindle in 2016 and have read hundreds of books on it. The cost per book at this point is in the pennies. It's not like you have to buy a new device every book, or even every few years.
Also I was very confused by the assertion that ebooks are a niche market. By the authors math more than 20% of people in the UK use e-readers to read on a regular basis. That seems like a very healthy market to me!
Do 20% really use e-readers? Sounds like a huge number. Do 20% even read frequently?
I'm not from the UK, and I'll admit my current reading habits are a sad excuse for what they were in my childhood and teens, so there might be some selection bias here.
Probably "20% of readers..."
I can say that out of the people I saw reading during my last beach vacation, almost all were using an e-Ink reader. They used to keep a small library of "beach books" you could read; that's gone. Casual readers have moved on to something else; people who read a lot have moved to e-Ink for outdoors.