Well the story book could be used.
I've seen several interface on
http://www.eqinterface.com that propose to use the story window to display the complete quests.
All those custom txt files have to be added in the everquest/storyline folder.
Writing in a txt file with C++ code is not that difficult. The main problem would be to know when and what to write in the txt file...
However this could be solved using the quest flags and a change flag (the change flag would be a fixed quest flag ). There would be a MySQL table holding the quest flags reference and the text linked to that quest flag.
The only question left is HOW to update the txt file
1) When zoning => Happens often so the txt file would still be updated. But what happens if you don't need to zone for completing the quest ?
2) Wen receiving xp (don't know if possible) would be ideal as it is just a flag to check.
That was my 2 cp