Dildos and other sexual aids are frequently mentioned in ancient literature and depicted on pottery, while didactic sex manuals were popular, as were more general advice books such as the Ars Amatoria
I am confused by "as were", I guess this is a kind of inverted sentence, maybe a regular order would be
as more general advice books such as the Ars Amatoria were
but I am not sure about my guess, can anybody help me parse this sentence?