I've had a few of the Absolute editions and I think Absolute Crisis on Infinite Earths is one of the best bargains ever. It has that great book with it that goes over all the crossover issues and appearances by the Monitor BEFORE Crisis. It's simply a gorgeous edition that I am so glad I bought.
I know it's not TRULY an Absolute edition, but the JLA-Avengers oversized hardcover is amazing, too.
I got one when it was published as a Christmas gift from DC Comics.