If you want to zoom to an object, like a text in a book, you just start the app and it will automatically load the camera inside it. You will then be able to magnify up to four times.
The button at the top will indicate the zoom level of the magnification - X1, for a standard view, X2 and X3 for two times and three times the magnification, respectively and X4 - for the full zoom that your hardware camera supports.
There is also a flashlight available, if your device has a LED light - it will help you see the small object better, if you are in a dark place.
On all devices it offers a X4 zoom - it automatically detects the maximum zoom level that the hardware supports and divides it into four equal intervals. It also supports auto-focus, high quality view, nice magnifier glass foreground(which can be turned off).