To be fair, I had listened to them many times before that, as they are one of my Dad's favorite pieces of music. (He's heard them preformed several times this year alone!) But I really discovered them my sophomore year of college, when I wrote a paper for my music history class on them. I used to put the album on repeat for hours on end, and never EVER get tired of it.
I am loathe to link to wikipedia, but their article on this piece is very fine. And I don't have time to write out the whole history here and now. The most remarkable and moving piece is the Duo Seraphim, a duet turned trio of angels singing about the Trinity.
Here's my favorite motet, performed by Seraphic Fire at the high altar in the cathedral of Mexico City. (They also have a video of "Laudate Pueri".)
And here are some fine recordings of it:
Tavener Consort (my recording): MP3, CD
The Monteverdi Choir (my dad's recording): MP3, CD
There is also a marvelous DVD of the 1989 concert in St. Mark's in Venice, (some of which is available on YouTube).
If you ever have the chance to hear the Vespers performed, please, GO GO GO. Otherwise, you can come over tonight, for I will be dedicating some of my evening to just sitting still, listening to this magnificent work of art and devotion--which to my mind has never been surpassed.