If the battery keeps draining quickly--try resetting the device:
http://www.kobo.com/help/en-US/artic...hd-or-kobo-glo
It also may be related to a corrupted book on the device. Might be hard to narrow down may be something you just added or were just reading.
I wouldn't jump to the conclusion that your HD is hosed just because the battery drained quickly a time or two. I've had this happen on various devices--kindles, sony readers, and nooks. Almost always resetting/rebooting fixed it. And if that didn't work a factory reset and reloading the content fixed it.
Good luck!