Ars Technica has an interesting piece today about the iPhone SDK, and the NDA that continues to withhold information about it from reaching the masses. While the problem isn"t that there"s a lack of documentation (however the current documentation isn"t always perfect), it does prevent many new iPhone developers (of which I am one) from getting the help they really need. Speaking from experience, there is quite a bit of information available, but almost all of it is in the Apple-provided documentation, and for someone who is only just delving into the world of Apple and iPhone development, sometimes the raw data just isn"t easy enough to get through.
The NDA has a big effect on the book industry, however. While many users on the Internet won"t stop at an NDA, book publishers will. So until Apple pulls this NDA off (or if they do), don"t expect to be getting that guide to iPhone development at your bookstore.