I’ve started reading ebooks on my Psion 5MX and sometimes like SE P800.
After downloading some stories in lit format from Fictionwise I converted to mobipocket format by first using Convert LIT and changing them to OEBF. Then with Mobipocket I created some I could read on my Psion 5MX.
I must say its very cool being able to open my Psion at exact the right page.
Some other useful ebook resources at this site.