I see others reporting issues downloading the app on iPhone 6. It worked for me, though it was slow to download. Anyway, this book is THE guide you want for a Kauai trip, and the app version is great. The information is fantastic and will steer you in the right direction no matter what your interest is on the island. I particularly enjoyed the hiking and beach sections. The gps feature (which works without internet service) is also great when trying to figure out tricky locations.
Thunder Hippo about Kauai Revealed 9th Edition