Many people have been reporting that apps they buy on the App Store will not install and/or launch. Apple said it has fixed this problem with release 2.1. If you are still experiencing the probelm, here are some things you can do which usually fixes it. Try these in this order until it is fixed:
1. Reboot your iPhone twice (hold down the power and home buttons for 10 seconds).
2. If that fails then you should re-download a fresh copy of the book. To do that, go back into the App Store (either on the iPhone or in iTunes) and click 'Buy Now'. Don't worry, if you've already purchased it then you will see a message asking you if you want to re-download it for free. You may need to delete the book first before you can download a fresh copy.
You can also see Apple's App Store Troubleshooting Guide which has some additional information. If you need further help you can contact Apple's Customer Support from the iTunes Help menu.
AppEngines sells electronic books for the Apple iPhone and iPod Touch. Each book comes complete with the text of the book and software to read it.
The book reader presents a single page at a time. To move between pages, simply tap in the top half of the screen to go back to the previous page, or tap in the bottom half of the screen to advance to the next page. You may also use swipe gestures.
In the top left corner is a button that allows you to search for text in the book. Tapping this button will display a search box to enter the text. Any text that matches will be highlighted in the book.
In the top right corner is a button that will call up the book's Table of Contents. This allows you to jump to any chapter in the book.
Use the pinch gesture to adjust the font size. Squeezing will reduce the font size, expanding will increase the font size.