Though there are a innumerable resources regarding the many facets of college admissions, I recommend a few books that I have found particularly insightful and helpful over the years. In no particular order:
The College Admissions Mystique by Bill Mayher, Farrar, Straus and Giroux, New York, NY, 1998
Creating a Class: College Admissions and the Education of Elites by Mitchell Stevens. Harvard University Press, Cambridge, MA, 2007
College Admission: From Application to Acceptance, Step By Step by Robin Mamlet and Christine Vandevelde, Three River Press, New York, NY, 2011
Admissions By Design by Lisa Fisher, Elevate Publishing, Boise, ID, 2015
The Gatekeepers: Inside the Admissions Process of a Premier College by Jacques Steinberg, Penguin Books, New York, NY, 2003
Looking Beyond the Ivy League: Finding the College That’s Right for You by Loren Pope, Penguin Books, New York, NY, 1995
On Writing Well: The Classic Guide to Writing Nonfiction by William Zinsser, Harper Collins, New York, NY, 2006