I was using this post to try and resolve this for my self and found all of the above options tedious to try and get working. Not sure why but none of them really got the job done for me.
However i did come across this little puppy!http://albite.vlexofree.com/reader
I've found this very easy to install and use with night time and day time options, bookmarking and the ability to change font size.
It also comes in a version designed to be used with the N8 so there's no little hoops that you need to jump through just to get it to work.
The files it can read are epub, txt and html. I have only tried epub so far but it seems to work brilliantly!
As for PDF, Some one out there may know of the answer to getting that to work on the N8 smoothly but it's certainly not me! i spent a day looking for options to use my pdf books even for ways of converting them,,,, alas boredom got the better of me and i just decided to re-download my books in epub/.txt
I hope you found this usefull happy reading!