Leverage the Pareto principle, get 80% of the benefit out of the key 20/30/40% of the concepts and exercises, and then move on.
This is hard to instrumentalize regarding difficulty. I find that the hardest exercises are likeliest to be skipped (after struggling with them for an hour or two), but it doesn’t follow that I can expect the easier ones (which I happened to have completed) to lie in that key 20%.
I like to randomly sample X% of the exercises, and read the rest; this lets me know later whether or not I missed something important. Simple rules like “do every fifth exercise” should suffice, with the rule tailored to the number of exercises in the book.
This is hard to instrumentalize regarding difficulty. I find that the hardest exercises are likeliest to be skipped (after struggling with them for an hour or two), but it doesn’t follow that I can expect the easier ones (which I happened to have completed) to lie in that key 20%.
I like to randomly sample X% of the exercises, and read the rest; this lets me know later whether or not I missed something important. Simple rules like “do every fifth exercise” should suffice, with the rule tailored to the number of exercises in the book.