If you want to become a better Wi-Fi engineer, then look no further to these 5 Wi-Fi books. We recommend having these books on your shelf and using them as reference. All of these books include a plethora of knowledge and have helped us in many situations where we need to refresh or learn a new topic.
The 5 Wi-Fi books are (affiliate links are used below):
CWNA Study Guide by David Coleman and David Westcott
CWDP Certified Wireless Design Professional Official Study Guide (PW0-250 version)
802.11 Wireless Networks by Matthew S. Gast
802.11ac: A Survival Guide by Matthew S. Gast