If you are referring to quantitative sociology (not mathematical sociology), maybe also look at Stephen Raudenbush (Hierarchical Linear Models, usu. applied in Educ), Yu Xie ("Demography: Past, Present, Future").
Urban/Social strat is a big big field. International comparison sounds popular recently (which I try to do too). To start with social strat, you may be interested in scanning Grusky's "Social Stratification", which includes most classic works in the field.