I read on mine too. I use Mantano though for my ebooks as it has collections just like a Kindle but you can also have Sub Collections. I throw all mine in a folder called ebooks then import them into Mantano and organize them.
I use my Clip Zip exclusively for audiobooks and Audibles. It works great.
I also use Akimbo on my SGP5 for Audiobooks and Audible app but I prefer my Clip Zip to it.