APEX Docs for iBooks
I'm not sure if this is new news or not, but you can download the APEX documentation in ePub format which can be loaded into iBooks.
To download the ebook format go to docs.oracleapex.com then click the download button for the appropriate doc and select ePub as the format.
Here's a screen shot of the APEX API docs in iBooks. I still prefer the online / HTML format but having the docs in iBooks helps when you may not have a internet connection.