Recently someone asked me to recommend books that will help understand creeds and confessional statements. I mentioned Philip Schaff’s magisterial (but outdated) Creeds of Christendom. Here are three excellent sources for your consideration:
Creeds of the Churches: A Reader in Christian Doctrine from the Bible to the Present by John H. Leith (John Knox Press). I hope it is still in print. If not, I’m sure used copies are available at the usual outlets on line.
Christian Confessions: A Historical Introduction by Ted A. Campbell (Westminster John Knox Press). (This one isn’t a reader; Campbell explains the creeds and confessions without reproducing them wholely. This would be an excellent supplement to the above work.)
With these three works plus “Schaff” you have everything you could possibly need to understand Christian creeds and confessional statements.