Compatability

How do I get the nook glowlight to be compatible?  I read tons of library e-book and bought the nook glowlight to read but it seems its not compatible with it.  I don't know why it wouldn't be.... I did download the android file transfer and tried doing it that way, but once I use it to download the book on the nook glowlight, it doesn't open the book on the device.  Please help! thanks!