  In this paper, we study the representation theory of the small quantum group
$\overline{U}_q$ and the small quasi-quantum group $\widetilde{U}_q$, where $q$
is a primitive $n$-th root of unity and $n>2$ is odd. All finite dimensional
indecomposable $\widetilde{U}_q$-modules are described and classified.
Moreover, the decomposition rules for the tensor products of
$\widetilde{U}_q$-modules are given. Finally, we describe the structures of the
projective class ring $r_p(\widetilde{U}_q)$ and the Green ring
$r(\widetilde{U}_q)$. We show that $r(\overline{U}_q)$ is isomorphic to a
subring of $r(\widetilde{U}_q)$, and the stable Green rings
$r_{st}(\widetilde{U}_q)$ and $r_{st}(\overline{U}_q)$ are isomorphic.
