Firstly it must be said that the Didache is not canonical. That means from a point of view of authority it needs to measure up to scripture to meet the tests of orthodoxy. On the other hand it represents a true insight into the life of the Christian Community and Church in the early post apostolic period. It is quite colear that the Eucharist and Baptism were both central to the life of the community, and the liturgy was not as fully shaped as it came to be by the conciliar period. What we cannot say is that it was universal, however we can say that we know that we now have some records of the late first or early second century Church. I used it the other day in talking about the Lord's Prayer, as they used it, because it shows an interesting insight. The Early Christian Church was I suspect much more eschatologically focussed than the contemporary Church is, and in part that was because they expected the eschaton at any moment. I think that the Didache helps understand how we got from the New Testament Church to the Church of the conciliar period. I believe that the Didache should be received as helpful.
We should take care about what we mean by authortitative... As Anglicans, for us nothing can trump Scripture, and although the Didache, the epistles of Clement and other such documents are exceedingly early and even in the orbit of the apostles, they aren't said to be the Word of God That being said in the Anglican worldview we adopt tradition as an essential interpreter of Scripture, and thus the Church Fathers and the early consent of the undivided Church, according to the Canon of St. Vincent of Lerins forms the lens for how we understand the truth of God's Word It follows therefore that the Didache functions as on the very highest of levels in terms of informing us how the apostles and their followers lived the Christian life and what the apostolic nature of the Divine Service, the sacraments, and worship looked like on the ground, so I would say it is very important
Personally, 1 Clement, the Epistles of Ignatius, Hermas, Polycarp to the Philippians, and a few fragments of Papias, I believe.
The Didache can be helpful at times, but like so many deutercanonical books it is rather redundant: an example is reading the Book of Wisdom after reading Proverbs. “But whoever shall say in the spirit, Give me money, or things of that kind, listen not to him; but if he tell you concerning others that are in need that ye should give unto them, let no one judge him.” (Didache 11:12) This passage from Didache is similar in context to Simon the Sorcerer who tried to buy the Holy Spirit (Acts 8:1-24), Annias and Sapphira hiding their money from Communal Church (Acts 5:1-11), and Paul the Apostle saying, “What is my reward then? Verily that, when I preach the gospel, I may make the gospel of Christ without charge, that I abuse not my power in the gospel.” (1 Corinthians 9:18), “Each one should give what he has decided in his heart to give, not out of regret or compulsion. For God loves a cheerful giver.” (2 Corinthians 9:7, “For if the eagerness is there, the gift is acceptable according to what one has, not according to what he does not have,” (2 Corinthians 8:12), and “But I did not want to do anything without your consent, so that your goodness will not be out of compulsion, but by your own free will.” (Philomon 1:14). If you followex the Pauline verses from Canon, you wouldn’t ever give a prophet money who begs for if because you would have alresdy decided in your heart what to give (2 Corinthians 9:7).