There are autobiographies and autobiographies - if it's by somebody under 30 or even 50 (and depending on who they are and what they've done as well) then I always ask myself why I'd want to read about what they've done so far. For example in that situation, had they written one, Mozart or Beethoven's lives would have been compulsive reading to see how it was for them at the time it happened.
People like, and I'm going to be very careful here in case I upset somebody, airhead clothes horses (or not wearing clothes at all...) who are famous for not being very good at what they're famous for, are obviously making some more money on the back of nothing very much so good luck to them, but I won't even bother to borrow their book from the Library, let alone waste money on the paperback version. Come back when you've done something worth writing about and in fact - get someone who can write to do it for you... officially!
People like Dawn French who I do admire and have had a career worth looking back on, then sure if you like them. Ulrika Johnson or Russell Brand? Hmm - if you like them and 'that sort' of clever clogs lad/ladette type thing then at least they can string a sentence together and are vaguely amusing occasionally. But really I think autobiogs are mostly, these days anyway, for show-offs who want to make money to tide them over after they've lost popularity.
If you've led a fascinating life then biographies are more the way to go as an outside viewpoint and fairly delving interviews probably get the subject looking at whatever it is they've done more intensely and objectively than if they're writing it simply as a memory - after all you're more likely to go easy with yourself on the rougher sections, gloss over the hard truths - or perhaps go too deep and too blinkered - with another person writing about you possibly get more 'texture' I think. Or a more rounded presentation anyway
Personally I don't read biogs (or autobiog) unless
a) the person is interesting to me and
b) dead, so you do get the whole life or most of it
is this being too picky?