Should I get the 4 volume set of the Mystical City of God, or should I get the Mystical City of God: A Popular Abridgement (a much shortened and far less costly version of the 4 volume set containing the revelation to Sr Mary of Agreda)?

I vote for the four volume version

I posted an introduction to another edition of Ven. Mary of Agreda's Mystical City of God wherein it is shown beyond a shadow of doubt that these revelations are duly approved and most worthy of praise:

http://www.cathinfo.com/catholic.php/Notice-on-the-Works-of-Ven-Mary-of-Jesus-of-Agreda

I posted an introduction to another edition of Ven. Mary of Agreda's Mystical City of God wherein it is shown beyond a shadow of doubt that these revelations are duly approved and most worthy of praise:

http://www.cathinfo.com/catholic.php/Notice-on-the-Works-of-Ven-Mary-of-Jesus-of-Agreda

A good friend told me there has hardly been another book that has had
more papal commendations, except perhaps the Imitation of Christ by
a Kempis and the Summa Theologiae of St. Thomas Aquinas.

Once you get going on Mystical City of God (unabridged) you will find
you can't put it down.  You'll look forward to the next chance you have
to read another installment.  Some of the sentences are so long they go
on for over a page, and when you get to the end of the sentence you
wish it had been longer.  Very strange experience.  

Reading the abridged version, you miss out on a lot of that, and you
get the feeling that something's missing.  Well, that's because there IS
something missing.  A LOT missing!  They whittle 5,000 pages down to
600 and guess what?  Something's missing.  

I also highly recommend the Mystical City of God - all four volumes. I wish it was even longer! It's probably best read from the beginning to the end in order; however, some people I know had difficulty in understanding parts of the first volume. If this should happen to anyone, instead of giving up altogether, I would encouraged reading the second through the fourth volume and then coming back to the first volume.