This book contains 26 literary works from the early Christian Church. These "books" were extant in the early Church, but when the New Testament was officially organized into Canon Scripture (officially accepted books), these were among those left behind. This book was originally published in 1890, reprinted in 1926, and again in 1979.
As one might expect with any collection of stories, this one is a mixed bag of good and bad stories. Some of these works are long and tedious, while some are short and don't seem to contain anything new. However, all of them allow a fascinating glimpse into the thoughts of various factions within the early Church.
Personally, I enjoyed The Epistles of Paul the Apostle to Seneca, with Seneca's to Paul, and the Epistles of Clement. I highly enjoyed this book and recommend it to you.