With the new release of APEX (or Oracle in general) it's always useful to re-read the documentation again, even if it's just the release notes and the installation guide...
I use my iPad a lot to read articles and books, especially when I'm offline it's very useful.
You can go to the site and read the documentation in HTML or download the PDF, but you can also download the documentation in ePub format (for examples the release notes of APEX 4.2).
When you click on the HTML link, the ePub link will appear for that document.
I find the ePub format useful as I can read offline and set some bookmarks for certain pages.
Hope you like this quick tip!