Well, what you can do is this:
1. Take your purchased .mobi file and convert it to a .epub file.
- This can be done on a site like Zamzar or using software like Callibre.
2. Take the converted .epub file and slap it into your Skydrive.
3. Get the Nokia Read App from the store, it handles .epubs well and PDF's fairly ok. (Was on an earlier post I saw this, thx WPC forums)
- If you cant see the Nokia app, could be due to your reagion (as stated in the post). Set your region to the UK and restart, it'll be there.
4. Open the Nokia Read App and import the .epub file from your Skydrive.
5. Read!
Hope that helps.