During the nineties two novels were released that further describe the Conflict portrayed in BI 1 and 2.

Battle Isle Saga. Eine Welt im Aufbruch - by Stefan Piasecki

Aristos Diener. Battle Isle Saga 02 - by Stefan Piasecki

I found both of them highly enjoyable (well, I was thirteen at the time). They are easy to get used on Amazon. Unfortunately, they never had an English release, afaik.

So, pick 'em up if you like the game.

Similarly, a comic was produced for the release of 'The Wilderness Missions' expansion for incubation.

I thought it was the bees knees when I found it inside my boxed copy. It sets up the scene for the first mission in the expansion quite nicely ;)

It is available for download here: http://scayra.free.fr/incubation/index.html

There is also a forum dedicated to incubation on this site, that has been pretty dead for a long time, but myself and a few others still post there now and again ;)

Forum seems dead, I mean down. I've posted some time ago there too.

I had the first novel in the expansion pack, which at the time to me was the best idea ever (and still is, why do the Mass Effect CEs for example not have the related novels packed in?)

I as well thought it was a good read (being around the same age as you back then). Not sure if I could go back though. Also I never knew there was a sequel. Any place you can read a synopsis on that one?