Little, except generalization, is added when someone contends all memoirs/autobiographies are written out of pure narcissism and hubris. Facilely lumping St. Augustine and Paramahansa Yogananda and the Pauline letters with Ben Franklin and Bernie Mac (Maybe You Never Cry Again) makes little sense. Could each have had other goals? My own written life anecdotes have been inspired by my wanting to record my life for my daughter, not out of hubris.
What is certainly true is that memoirists are interpreting their OWN LIVES. Well, of course! That is the intriguing part: they (and I) place their lives within a social and historical context and construct a personal narrative. It is, after all, we who interpret our own lives. The interest is HOW WE SEE OURSELVES. Aren't we fascinated at how misanthropic Richard Nixon saw himself?
So, for Barack Obama and his two memoirs, the import is how he sees himself, how he fits--or not--within a social-historical context. And what he constructs as HIS narrative. In this case, it is not important whether he is narcissistic (in a country--America--known for its inherent, unparalled narcissism), the self-reflexivity and narrative themselves are what are important. Factual "inconsistencies"--I'm sure they will be aired. Still, his story, as self-constructed, in which he reflects upon his ambivalences and confusion, but also his deep family connections, are refreshing. (Compare Sen. McCain's self-appointment as "maverick.)
Personally, I have never been inspired by mere politicians (other than possibly the "story" of Abe Lincoln). Obama's "story," at least as he tells it, is a story for America and fulfills some promises made long ago.