is it correct to
> conclude that the vtkWedge cell type is documented incorrectly, and that 
> the current picture in the manuals should have nodes 1 and 2 swapped as 
> well as 4 and 5 swapped?
Correct. This will be updated in the next version of the book.
     2
    /\
   /  \
  /    \
0-----1\
  \     /\5
   \   /  \
    \ /    \
     3------ 4
Mathieu