There seem to be two questions here. First: 'what are some eye-opening reads'? Second: 'what are some good philosophy books?'

The fact is, "eye-opening reads" really depends on the eye, and without much context, it's very difficult to give recommendations.

So I'll name two books that were 'eye-opening' for me AND are good philosophy and another that is just 'good philosophy.'

J. S. Mill's On Liberty. Read it. It's short. It's poignant. Don't not read this book.

Beyond Good and Evil by Nietzsche is required reading. if you like it, check out the viking collection of works by him and read his wikipedia page. You'll get a sense of what else you'd like to read from these two sources.

The groundwork for a metaphysics of morals by Kant is a great introduction to his way of thinking/reasoning and deals with an important matter--the possibility of a moral system. This book is a good introduction to a way of philosophizing very different from the others--Kant aims to be deeply systematic and specific. While not eye-opening, 'sexy philosophy' or quite 'enjoyable,' GMM is a relatively short read and a worthwhile thought-journey.