Step 1
After launching iTunes on your PC, iTunes will automatically detect your local ePub eBooks and display some of which in Books Library. To add the eBooks in Book Library manually, you can choose File> Add File to Library… or File > Add Folder to Library… to add local ePub eBooks or folder (must containing ePub eBooks) to iTunes Book Library. Also you can drag and drop local ePub files directly into the iTunes Books Library. After put eBooks in iTunes Book Library, you can easily change epub book cover and some other information before transferring to your iPad.
Step 2
Use USB cable to connect your iPad to your PC. And in iTunes, you can see your iPad in the source list under Devices.
Step 3
Click on your iPad in the source list under Devices. Then click the Books tab at the top of the window. Here you can choose whether to sync all books or selected books. If you choose All books, all the books in the Books Library would sync to your iPad. And here we choose Selected books, and choose the special book for syncing. Then click Apply button, you can have your selected eBooks successfully synced onto your iPad.
Check your iPad, and the local ePub eBooks are shown on your iBooks shelf. Quite easy, right? Please note that you can also transfer ePub eBooks to your iPad, iPhone and iPod touch (with iOS 4) from either PC or Mac via iTunes, and I just take iPad connecting with PC for example above. All the syncing process is the same.
