Bricked device

If you've the opportunity, I wouldn't risk.

Delete the downloaded file, then restart the update procedure with a more reliable and fast wifi network ("borrow" one from your friends, or ask for help at an Apple Store or Authorized Service Provider.

Regards

Giulio

EDIT: Do not forget to create a full backup before restarting the update process.

If the download has successfully “verified”, it should be safe to proceed. That said, if you have any doubt, starting again will do not harm. Keeping your iPad within good WiFi reception will help with minimising the time required to complete the update.

Ensure that your iPad is connected to its Power Adapter for the entire update process. This serves two purposes:

1) The WiFi connection is kept active throughout the update process; if operating on battery power and not kept active, the iPad will automatically “sleep” - interrupting the download process.

2) Keeping the iPad connected to external power provides a redundant source of power through the update process. Whilst the update should proceed with the battery showing at least 50% battery charge, reliance upon the battery alone during the update is unwise. If the battery should fail during the power-hungry update process, whilst the OS is being “flashed”, the iPad may not recover.

It's a good practice to back up your device on a regular basis (ALWAYS before an update process).

Regards

Giulio