Might consider, say, Sidney Siegel, N. John Castellan, Jr. 'Nonparametric Statistics for the Behavioral Sciences, Second Edition', ISBN 0-07-057357-3, McGraw-Hill, New York, 1988. So, "nonparametric" means make no assumptions about a probability distribution based on parameters . Or, call the material distribution-free . E.g., get to see about resampling plans -- tiny assumptions, really simple, darned cleaver, quite…
Huh? I have that book, and it's nothing like ISLR, at all. It's a good book, but ISLR covers topics such as gradient boosted trees, survival analysis, GLMs, etc. Nothing at all like the book you mentioned. If forced, you could say ISLR is more focused on prediction, not inference or hypothesis testing.
Nonparametric Statistics for the Behavioral Sciences,
should make a good contribution to statistical learning. Some of the techniques are so robust, i.e., need such meager assumptions, that they should be especially welcome in automatically applied AI (artificial intelligence) applications.
Actually the book ISLR, Introduction to Statistical Learning, does claim to cover
"Resampling methods"