I really love my iPhone - taking pictures, listening to music, playing games, staying organized. Love it.
And I have the 4S model so it includes the lovely voice assistant Siri...whom I would love more if she acted less like a petulant teenager and more like an assistant. Because we definitely have a failure to communicate.
Talking to Siri by Erica Sadun is a short, small book, only about 150 pages and not quite mass-market paperback size, and it is very helpful. I learned how to phrase questions using Wolfram Alpha-style queries. I learned how to set places like "home" so I could tell Siri to get me directions to home. I got the hang of having Siri make appointments for me.
And I learned a few fun things. For instance, Siri is an "it" not a "she" because different markets have a different voice - the US has a female voice but the UK has male, apparently. And you can make Siri give you funny answers.
Just tell it you need to dump a body or say "Beam me up, Scotty." The answers are all deadpan, of course.