Most any device with the exception of the Amazon Kindle support the Adobe ePub format. The EPUB format can be used with many different devices since the format is based on an open eBook standard developed by the International Digital Publishing Forum. If you do not own a Kindle and want to use the digital eBook you download from Offworlders.com then EPUB is the format you want.
Click here for the official list of compatible eBook devices from Adobe Software.