The term dual-tapping refers to the use of multiple apps to access different portions of the same application.
When used in conjunction with “tasking,” this is a common way of using multiple apps simultaneously.
The app that is using the most CPU while multitasking can be the fastest one to the right, the second to the left, or the third to the top.
If you are trying to read a book on your phone while multitasking, this is how you will get the most out of your battery.
If you are reading a book while multitapping and you want to switch apps quickly, then you might want to look at a multi-window app like iBooks, which allows you to read two separate books simultaneously.
However, this approach is much more difficult when you have multiple apps on your screen.
Instead of having one app to multitask, you need to split your screen into two, then switch between the two apps.
This can make multitasking a little tricky, especially when you are switching apps frequently.
This video from iBooks will walk you through the process of switching apps quickly with an app called iBooks for Windows.