A much better book on McCarthy is Arthur Herman's Joseph McCarthy: Reexamining the life and legacy of America's most hated Senator. Herman comes to very similar conclusions but his book is well written and interesting. It's about 1/3 shorter too.
Actually, Evans’ book is better researched and sourced.
However, Evans’ book contains some major flaws which I briefly addressed in my webpage here:
https://sites.google.com/site/ernie124102/cpusa/mccarthy