Ok, so spoilers ahead.
Alright, so there's this one guy who survives the tribulation who believes, (TAKE A GUESS) and like he ages but doesn't die, which is weird. And like there was like two people who were married to each other before they died, but somehow they don't feel any affection for each other...after they come back to life. And then there are people who are born during the millennium, these new characters who have kids, and these weird salvation stories of people dying at 100 years if they don't believe in Jesus. And like there is guy who was married twice who is still alive in his natural body running around with his two resurrected wives running a ministry...I am not making this up.
I might be a little fuzzy on this one, it's been several years since I read Left Behind. I don't think the millennium will be quite like that, mostly because the closer you get to God, the better your relationships with other people become, generally speaking. (Unless you are in a bad crowd or have bad apples for the key relationships in your life, but these were Christian married people.)
Also I think resurrected believers with glorified bodies will be a LOT more awesome than Kingdom Come made them out to be, and likely inspire envy in their unressurected counterparts. That's just a theory of mine, so don't quote me on it, but yeah.
In any event I have no doubt that the millenium will be weird - we have people like Moses and Abraham walking around with people from the 21st century (and maybe beyond???) unressurected Christians that survived the tribulation, Christians born in the millenium who don't know anything different - it will be a whole bunch of colorful relationship chaos beyond anything we could ever imagine. But it will be fun.