You can use many of the reader applications out there. I am not sure what nook applications are out there but you can certainly use kindle on the IQ.
The IQ comes with its own reader. I am now using moon+ reader and overdrive (for library books). In the past, I have tried Laputa, Aldiko and FBReaderJ.
Have a look at this link. It outlines some (not all) of the possible apps:
http://blog.the-ebook-reader.com/201...allation-pack/
The site mentioned that Nook apps do not work on the IQ.
Cheers