Along with volume 4 of the Ancient Christian Writers Series (Didache, Epistle of Barnabas...) these writings are second only to Scripture itself in early Church authority. In fact before the creation of the New Testament canon, the 1st epistle of Clement was widely regarded as Scripture.
This is a must-read for Catholics, Eastern Orthodox, and anyone who wants to know anything about the early Church.
These are very good books to read as they give an insight into the teachings of the early church. They are in every respect akin to Gospels.
Don't be put off by 'Catholic' reviewers, who have in fact ignored that the Orthodox Church is descendant from these thinkers as well (hence it also is 'Catholic' - which just means universal). Thus when Clement urgres obey bishops he means ALL the bishops of the Christian community, not just the Bishop of Rome!