In a recent comment, Dawnelle recommended the book The Five Love Languages by Gary Chapman. I wish to heartily recommend this book as well.
The basic premise is that the way we show love/affection tends to fall into one of five basic categories, here presented in no particular order:
1) physical touch
2) words of affirmation
3) quality time
4) acts of service
5) giving/receiving gifts
People typically have one or two primary "love languages" -- things that mean love and affection to them. Let's say that the primary ways I give & receive affection are through physical touch and words of affirmation, and let's say that the way Hannah gives & receives affection is through acts of service and gifts. We both might spend years giving each other what what we thought was expressions of love, but miscommunicating badly. I might be starved for touch and kind words, and sick to death of getting wallets and shirts and having the house painted and dusted and my closet reorganized. Hannah might be tired of me pawing at her all the time and always wanting to talk about things and getting my feelings hurt by her silence or unkind words, while starving for a little present once in a while and for me to show I cared by putting together a thoughtful date/surprise or keeping the lawn mowed and her appliances working. Both of us might feel like we're trying really hard to love someone who doesn't love us back. I'm just saying, this could happen.
Another book, for guys: If Only He Knew, by Gary Smalley. Strong Christian bent, but useful to anyone, I think. Not a feminist-pleaser, since it presumes vast gender differences and traditional family roles; it's the polar opposite of the "treat everyone the same" approach. I think the value of the book is in educating men about how many women think and feel about some things, and ways they can make their wives feel loved and cared-for rather than put down, neglected, or unloved.
And one more, for women: Proper Care and Feeding of Husbands, by Laura Schlesinger.
I have problems with Dr. Laura -- I find her inconsistent, judgmental, unhappy, and borderline misogynist -- but I like her standards on personal responsibility, and in this book I think she's more often right than wrong in describing what husbands want and how they feel.
This book has been savaged (often by people who haven't read it, including Hannah & her girlfriends). The typical accusation is that it portrays men as simple-minded and sex-crazed -- that all we need to be happy is a hot meal, less nagging, and more hanky-panky. But that's not actually what it says. The book *is* like Dr Laura -- unsubtle and overstated -- but a few of its fundamental premises are correct: specifically, that men's needs are typically simpler than women's, and that high on the list are a peaceful home (ie, less nagging/ragging), more appreciation, and more sex.
Like any book, you should read with some amt of skepticism -- measure it against your own world-view, and take what you think is useful from it. There's no rule that says you have to follow any of the book's recommendations, or buy 100% of its portrayal of men, but if you seriously want to understand more about men, this book is worth including on your list.