I love these designs, and this whole design era. I highly recommend JC Carbonel's French and European Spaceplane Designs, 1964 - 1994 in the French Secret Projects book series. Conveniently, the back cover blurb is even printed over a picture of the STS-2000, which is covered thoroughly. There's a lot of art and design material that I'd never seen before, and this really helped clarify the relationship between some of the confusingly similar designs like the STS-2000, Taranis, and the AGV.