I'm trying to understand how and why "elite" colleges (not necessarily just Ivies) select students to admit using not just academics, but also "Extra-Curriculars" (ECs).

I came across this book "The Chosen: The Hidden History of Admission and Exclusion at Harvard, Yale, and Princeton" by Jerome Karabel
I won't read this 738 page book, but the reviews give a good idea of the history.

Can anyone suggest anything more succinct to read about this baffling topic?

Does anyone have any insight?

I imagine a discussion on this topic could get quite wide ranging but I'd specifically like to hear actionable information and actual experiences.