Unless you are reading a topic you are already familiar with, reinforcement of an idea helps you to examine a concept from different angles and to solidify what is being discussed.
If everyone fully absorbed and understood everything they read, schooling could be completed years in advance.
Some people want more or less evidence based on their level of skepticism or critical thinking, while others want more evidence to reinforce the soundness of their inferred position on a topic, especially if it's a topic unfamiliar to them. Other people are under time constraints and just want the key points and a brief presentation.
This should be dealt with by pressuring the publishing industry not to inflate books and fill them with fluff. This could be done by not buying these kind of books, and publicly shaming publishers who engage in this behavior. It's easier in non fiction books since the amount of fluff in fiction books is a more subjective matter.
You can't shame them into buying books they can't sell.
How much electricity does it take an LLM to summarize a book? I'm sure the carbon emissions involved are trivial, and if they aren't, I've always been of the belief that (like eating meat) people are going to do what they want to do regardless of the environmental cost, so it's better to focus your ire on reducing the environmental cost. The problem here isn't using an LLM to summarize a book, it's that we've got a power grid fueled mainly by fossil fuels. (That is a problem that will fix itself in no time anyway now that renewables are cheaper and the gap is widening.)
This applies equally to Sci-Fi and fantasy doorstopper novels. At least those have interesting filler—sometimes even better than the main story.
So you get a decade of "business nonfiction" bookstand fodder which is claims with high shock quality but often not relicable, mixed with anecdotes, to signal the reader's self-declared learnedness.
Combine this with the long-tailed nature of the statistic "the average American only reads one book a year" and it's frightening. I think Scott Galloway said sales of his e-book are >10x more than his paper book.
And during Covid lots of people got exposed for having fake bookshelf backdrops.