I first read this book shortly after it was published. It has lived rent free in my brain ever since, so I decided it was time I reread it. 
Most significantly I was obsessed with how gender and sex are portrayed in this book. You are the gender that your brain says you are, and you just occupy male or female bodies for a time.  For my non-binary and trans friends, this seems pretty ideal. Don’t feel like your body matches your identity? Hop to a new one. And while I don’t have “penis envy” I find the idea of being able to experience sex from both sides to be delightful. It would also be nice to be able to swap bodies to match the needs of a specific task/job, or due to exhaustion when a task/job must continue.