Turns out a lot of that was a "dream" after all.
This is more stuff from Maraniss' book on Obama.
Turns out that there were several "fantasies" in the memoir that are easy to document. This article mentions 9, but another article tallies 38. The "composite" NY girlfriend seemed pretty harmless ... but some of these others would really change the "narrative" of his family roots.
An article by Ben Smith then says that it's not Obama's fault if people believed these misrepresentations. I'm not sure I can make sense out of that.
Why would a public figure (this was written just before he ran for Illinois Senate) publish stuff like this that could easily be disproven? By the time he wrote this book, he was not a pot-smoking teenager anymore.