Out of all the books I've read thus far, I think Juul's half-real was the one that improved my understanding of games in a very tangible way. A lot of the metaphysical stuff is very interesting but it generally has more to do with metaphysics than it does video games. That is, video games are a useful tool for discussing ontology (it's the basically study of reality and how things relate) because of the way the simulacra reflects on the user, in reverse there are moments but there aren't really enough games engaging with the concept for it to be a viable approach yet.
Juul's book is concerned with charting different kinds of game design rules, particularly emergent vs linear structures. He's a coherent writer but there are a lot of graphs and because the book was coming together in 2004-2005 he doesn't have all the rich examples we have today. The book defined a lot of concepts I was always aware of but never really had a term for. Things like when a game explains how it works and when it doesn't, branching design trees, yada yada.
If you're a liberal arts major with no formal training in tech or games, this is a pretty good starting place.