What are your thoughts on an author writing a book from the perspective of someone of the opposite sex?

I started a book a while ago it’s been put on the back burner in favor of my latest project wherein I am writing from the perspective of a male, and I am a female. The book takes place so far into the future that genders have been redefined or abolished, depending on how you look at it but the fact still remains that there are many things I don’t know about how a male body feels or reacts.

With this in mind, can you tell me what you think about books in which the author writes from the perspective of someone of the opposite sex?