Whether you have already purchased your iPad, or intend to have one in the near future, you may want to look into the Apple iPad user manual. The manual does not come in the box but is available below as a PDF file.
The user manual covers everything that you can do with your iPad, starting from checking your mail to syncing with iTunes, and changing settings.
Organized in 17 chapters and two appendices, this one is a definite helper for both beginners and iPhone/iPod Touch users. The user manual can be downloaded here.