What is the Trinity?

the long version

The purpose of this book is to supply a lack in the means available to the Christian who wants to widen his religious knowledge. There is an urgency for a better understanding of the Trinity in our age, even of the need to contemplate its mystery. To be overcome with wonder before this God who reveals himself to man, before the life of God himself, that life which he possesses as Three-in-One, that life which he freely gives to us; to find in contemplation of this mystery the source of all spiritual life and the mainspring of all action.