Geom_Surface from TopoDS_Shell

Hmm...
1. TopoDS_Shell: 1 occurence (no any good info).
2. Geom_Surface: 0 occurences.
3. Surface - n occurences (no essential info).

More then - I looked throgh all *.hpp headers :) for TopoDS_Shape - no any direct method like with wire.
It seems that engine suppose that only faces may be a continues surface.
Possible it is too hard to recgonize all situations while converting shell to surface.

I'v finded interesting fact:
If faces is connected in some direction correspond Surfaces (to each face) have continue paramaters (for exapmle in u-direction):
0..0.5 - to one face, 0.5..1 - to the second face.

But I solved my task changing algorithm (which is not need to convert set of faces to continue surface).

P.S.
And it is not politely to throw man to documentation. The same number of chars which you wrote can simply describe the direction of search.
The right answer possible sounds:
"Tra-l-ala - for more details see documentation *.pdf".