PM will give you insights into the psychological things that actually drive "real" desire and passion in a relationship and stresses the fact that "marriage" notoriously causes a "meet-in-the-middle" thing to occur where you ignore / hide your true self to become more integrated with your mate. And despite the idea of "soulmate" and "two becoming one", this is actually a bad thing.
Have you ever met someone from another part of the country who still has their regional accent? Have you ever met someone whose accent adapted to the region they moved to? Chances are that the person who still has their accent has "more personality" than the person who adapted...it's like a "strength of character" thing. This type of thing happens when we are married...we lose the "accent" that drew us together in the first place because we assimilate each others'.
So, I would say the most important concept in PM is "differentiation" which stresses the absolute importance of keeping your own identity outside the marriage so you can have something to bargain with inside the marriage. Too often, we give it all away right off the bat.
Understand that PM turns almost everything we "thought" we knew about relationships upside down. You will find yourself scratching your head at times and re-reading a section with a confused look on your face. Try to keep a very open mind. You guys might not have enough "years" yet to recognize the relationship dynamics described in PM but it will at least give you something to look for. I wish this had been required reading before I got married.
Anywhere is walking distance if you have the time
-Steven Wright