Newport splits work in two: the kind that demands uninterrupted attention and produces things nobody else can produce, and the kind you can do distracted, which creates no new value however much of the day it eats. His claim is that the second crowds out the first by default, not by decision.
What I did with it
I stopped calling it "an hour a day for email and admin" and started calling it a shallow-work budget. Renaming it changed the conversation I have with myself: a budget runs out, and what is left over does not get done today.
Inside that budget I reserved a slice for the promise to reply within one business day. That promise is a commercial commitment, so it needs its own slot; without one it gets kept at the expense of everything else.
And I added hours of concentrated work to the monthly review, next to the usual numbers. It is the only way I found to notice, in time, a month where I was very busy and nothing moved.
What I left out
Much of the book. Newport writes from a tenured academic post with no clients; the isolation recipes — disappear for weeks, do not answer email — are not available to anyone who makes a living answering on time. What does transfer is the principle: left uncapped, shallow work takes everything.