I bought this book after loving Michener's Hawaii, hoping for a similarly wonderful reading experience. I was disappointed. The best I can say is that I learned some things--the book takes you around Afghanistan in the 1940s, introducing a variety of places and cultures and including pertinent historical information--and that's why it gets 2 stars despite being otherwise awful.
This book suffers from the twin problems of an uninspired, meandering plot and a narrator who is one of the most unlikeable characters I've encountered in quite a while. First, the plot. The book is marketed as a tale about a diplomat (Mark) searching for an American girl (Ellen) who married an Afghan, then disappeared. But the first 100 pages of the 400-page book are all about everyday diplomatic life in Kabul (there isn't even any conflict to keep readers entertained), and we're past the halfway point before Mark bothers to ask Ellen's husband about her whereabouts--despite the fact that everyone has known the husband's location all along and he has nothing to hide! A plot that serves mostly as an excuse to explore a setting can work, but in a novel, descriptions of the geography and culture can't just replace interesting events and dialogue.
For that matter, all of the characters work to avoid plot advancement: before actually sending someone to search for Ellen, or even talk to her husband, the U.S. government interviews all of her former boyfriends and roommates in an attempt to figure out "what was wrong with her" that made her marry an Afghan in the first place, and there's much serious discussion of whether Ellen's hometown was objectively a bad place. (If Michener intended to poke fun at the investigation this might have been clever, but unfortunately he seems 100% serious, providing some unintentional comedy.) If missing-persons investigations are conducted this way in real life, I'm surprised anyone is ever found.
Then there's Mark. He's a jerk. For instance, he theorizes that Ellen chose her unusual lifestyle because she can't have kids, resulting in--wait for it--"a barrenness of spirit." I haven't even gotten to his creepy relationship with the Nazi refugee Stiglitz, a prime example of character relationships that make no sense. Mark is Jewish (and prides himself on having "table manners" despite that fact, as if Judaism and etiquette were mutually exclusive), and he veers back and forth between wanting Stiglitz dead for the atrocities he committed and wanting to be his friend. I can't imagine why, since Stiglitz--like Mark and most of the other characters--is utterly unappealing and unsympathetic. Oh, and it's worth mentioning that Mark has random, plot-irrelevant flings with most of the female characters in the book. Give me a break.
Ultimately, this book was a huge letdown. It read like a travelogue--dull, with little plot or conflict and uninteresting characters. It felt incredibly dated (I suppose I should have known that from the plot summary: it is, after all, a book about a white man traveling around an Eastern country, getting "closer to earth," and attempting to "rescue" an American woman he has no reason to believe is even in danger). Unfortunately, after Caravans, I will be wary of Michener books in the future. For those who want to learn about Afghanistan through enjoyable fiction, I'd recommend Khaled Hosseini's works instead.