Nonverbal imperative sentence?

Question

James Clear in his recent book Atomic Habits suggests some examples of habit shaping(in this case for becoming an early riser) and says:

Be in bed by 10 p.m. every night (reading a book, talking with your partner).

My question: Is "reading a book" an imperative sentence here, so means: "Read a book before sleeping!"?

He had said before:

In one study, scientists instructed insomniacs to get into bed only when they were tired. If they couldn’t fall asleep, they were told to sit in a different room until they became sleepy. Over time, subjects began to associate the context of their bed with the action of sleeping, and it became easier to quickly fall asleep when they climbed in bed. Their brains learned that sleeping—not browsing on their phones, not watching television, not staring at the clock—was the only action that happened in that room.

I don't know if there is a contradiction or maybe I misunderstand the meaning

of nonverbal sentence(reading a book, talking with your partner).

Could you pleas explain it to me?

Answer 1

No, "reading a book" is not imperative. It is a non-finite clause, here acting as an adverbial, qualifying "be in bed".

Yes, this does seem to go against the implication of the longer paragraph you quote.

Answer 2

The sentence is not entirely grammatical, at least, not the parenthetical, but its meaning is fairly clear.

The sentence could be written in a more strictly grammatical way like this: "Be in bed, reading a book or talking with your partner, by 10 PM every night."

The idea behind including that parenthetical, rather than writing the sentence I wrote, would seem to be that the main instruction is: be in bed by 10 PM. "Reading a book" and "talking with your partner" and examples of things you might do in bed at 10 PM.

So, a more accurate (accurate grammatically and in meaning) might be, "Be in bed by 10 PM every night. Once you're in bed, you can read a book or talk with your partner. The important thing is to be in bed."

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This advice does contradict the advice given to insomniacs, which you've quoted. Insomniacs are instructed to do nothing in bed but sleep. There could be all kinds of reasons for this contradiction, for example, this advice to read or talk with your partner might not apply to insomniacs.