Author here. Yes, I agree that reading for two minutes here and there is not that effective, but in my opinion, as little as 10 minutes of reading helps me make progress. The story is already loaded in my recent memory, so it's quick to switch context and immerse myself back in the book, even if I only have a short amount of time.
Reading multiple books at the same time helps with this. The level of concentration required varies by book and personal experience. I can set aside a larger span of time for more complex books and read more lightweight stories for the rest of the day.