It is the earliest and most important document on the early Church and the most complete research on it is in the wonderful book I just obtained (984 pages) : The Didache: Faith, Hope, and Life of the Earliest Christian Communities, 50-70 C.E.

It is clearly an important addition to your Catholic library.

Some great information about it can be found at http://www.didache.info/AaBookPaulistDidache.htm