  We study the discretization of an elliptic partial differential equation,
posed on a two- or three-dimensional domain with smooth boundary, endowed with
a generalized Robin boundary condition which involves the Laplace-Beltrami
operator on the boundary surface. The boundary is approximated with piecewise
polynomial faces and we use isoparametric finite elements of arbitrary order
for the discretization. We derive optimal-order error bounds for this
non-conforming finite element method in both $L^2$- and $H^1$-norm. Numerical
examples illustrate the theoretical results.
