www.omgubuntu.co.uk/.../...ok-reader-software.html

www.linuxquestions.org/.../how-to-install-program-to\
-palm-tx-with-jpilot-618608/

Have you tried Calibre? It is in the repositories.

Calibre works perfectly.
Is there an option to mark the line, a kind if bookmark?

Yes. It bookmarks. Look for the star icon along the left edge of the reader.