We consider standard graded toric rings $R_Δ$ whose generators correspond to the faces of a simplicial complex $Δ$. When $R_Δ$ is normal, it is shown that its divisor class group is free. For a flag complex $Δ$ which is the clique complex of a perfect graph, a nice description for the class group and the canonical module of $R_Δ$ in terms of the minimal vertex covers of the graph is given. Moreover, for a quasi-forest simplicial complex a quadratic Gröbner basis for the defining ideal of $R_Δ$ is presented. Using this fact we give combinatorial descriptions for the $a$-invariant and the Gorenstein property of $R_Δ$.