Read a book until you get one compelling thing out of it, then put it back in your reading queue
I’ve noticed a way I’ve read books is to reach a “Huh!” moment, think deeply about the book for several days then lose interest in the book. I have made the decision to internalize this as a really positive reading strategy.
A lot of the reasons this can happen really do mean you have finished the book. One is simply that not only did you reach the thesis of the book, you challenged and internalized it. The rest of the book is denouement or details now. One of the functions of details is to promote internalization of the thesis and this function is now used up. And you’re usually reading a book to capture its thesis, not to learn its supporting details.
At this point you should switch to learning by writing, instead of learning by reading. Write a one page review of the book or an outline summary of what you learned so far. You don’t need to finish the book to write a personal review.
The book may still be quite valuable. But it is probably less valuable after consuming the thesis. So this is a pretty natural point to lose interest in the book until further notice. As a bonus you now have fresh material to read should you want to revisit the book and rekindle your understanding of its thesis. Why ruin that with a dry, useless read? In other words, you can count the book as “read” now. Extracting the thesis from the book surely counts as having read it more than the literal act of reading all of the pages.