I've read about this in my Computer Gaming World magazine for June '02.
Here's some good stuff:
"The first step is to bring the look of the series up to modern standards, and the new graphics engine should have no problem in this regard. Lara alone will be made up of about 5,000 polygons, a tenfold increase from earlier games. This monumental leap in the level of detail will carry over to the architecture and the foes she encounters."
According to this, the new story is more complex than the others. It says that Van Croy, Lara's mentor takes her to Paris to track down 14-century painting for a client. Van Croy dies and she is framed for the paintings. And thus begins the adventure. Sounds interesting, I guess.
"Overall,
The Angel of Darkness is likely to appeal to a much more mature gamer."
(I wonder what that refers to...

)
Looks like a promising game; hopefully it will revive the series...