She wrote her book when the SDK was still NDA and before it used IB. Many, many changes occurred after that time.
I think there are two styles for the UIProgressView. The default which is referenced as UIProgressViewStyleDefault, and the one you are referring to is called UIProgressViewStyleBar.
those are set as the following yourUIProgressView.ProgressViewStyle = UIProgressViewStyleBar;
or
set nothing for the default.
It's UIProgressBar, a private subclass of UIProgressView.
You can use it in this way, but Apple might reject your app:
[[NSClassFromString(@"UIProgressBar") alloc] initWithFrame:CGRectMake(0.0f, 0.0f, 100.0f, 90.0f)];
For what it'a worth, another way of accessing the old-style progress bar is to create a UIProgressView control in the usual way. As of iOS 4.1, you can get the old appearance by setting the progress view's style to the undocumented value of 100.
This avoids using an undocumented class, or even calling undocumented methods. However, I'm sure Apple still won't approve.. ;-)
Dave