After watching the movie and reading the annotated screenplay I decided to read the original book. While I'm very glad Armstrong decided to allow an author to tell his story, I didn't find the book terribly good. It was never quite a hagiography, but you were always aware that it was an authorized biography, and while I don't think Hansen whitewashed anything – I think Armstrong was as nice and as calm as he appears and doesn't appear to have had an ax to grind – the reticence of the main character doesn't help make the story interesting.
Which makes no difference to the story – what Armstrong did is all the story any author ever needs, and Hansen does do history a great service by asking Armstrong many of the questions historians wanted to know. Did it happen this way or that way? What were you thinking? So while the repeated insertion of "Armstrong says that …" was slightly jarring, it made it a more interesting read, because this is the one place where Armstrong's reticence wasn't an obstacle – if the question was asked, he answered it. But deathless prose it isn't.
The book did make me sad I never got to meet Neil Armstrong – I would really have liked to. My absolute favorite part of the book was was when he was an older man and was having dinner at a friend's house and after dinner, the host's small daughter (or granddaughter) took her family's visitor around by the hand to show him her stuff. She was narrating all her toys and books and pointed out that she had a book about the moon landings, and chattered on that the first man to walk on the moon was Neil Armstrong, and then brightened and said "and your name is Neil Armstrong too!" And kept talking, it never having occurred to her that the old gentleman was the same man. I absolutely love that story just for the smile it must have brought to his face.