Read Edith Wharton's 'Age of Innocence' first. It portrays New York Society in the previous decade and will be a good insight into this picture of the 1880s.
I haven't seen the new series but the Edith Wharton book presages the social changes this series is based on.
Found this series which seems to be an American version of Downton Abbey. Lavious sets, gowns, jewellery and beautiful ladies. Pure escapism. Something we all need in this troubled world at the moment.