I remember writing quite some text for the official website of Ego Draconis. There's a story summary of the events that take place from Divine Divinity up to Divinity II (which you can also find in the original manual) and there's quite some detail about certain characters, creatures and regions.

Also, if you gathered some of the in-game books, you'll find a lot more story/background concerning the history of the Dragon Slayers (parts I to III), the history of the Dragon Knights (parts I to III) and the history of the Damned One (parts I to VI).

I am in blood
Stepp'd in so far, that, should I wade no more,
Returning were as tedious as go o'er.