LHoD is the one about gender; Dispossessed is the one about political/economic structures.
My mom tried to get me to read The Dispossessed when I was in middle school. It didn't take--I had an advanced reading level, but it was just a little too over my head. When, as a college grad, I finally did read it, I understood why she had been tempted to try it on me so young; it's an amazing book, and still radical in 2009. The deconstruction of the absolute idea of gender has now been absorbed to some degree in the US, enough that LHoD no longer seems so revolutionary (even though it was), but serious treatment of the ideas of anarchy, society without possessions, and society without authority still prompts us to stuff our fingers in our ears and sing "LA LA LA LA CAN'T HEAR YOU you Marxist, you."