This is a good article about what it is like to fly as a passenger from LA to London via KEF on WOW at a very low airfare. It is good to hear they try to be upfront about the add-on fees to manage expectations:
http://www.businessinsider.com/what-its-like-to-fly-on-budget-airline-wow-air-2017-1/#according-to-dozer-not-all-wow-seats-are-created-equal-7