If you want to get (nearly) everything that was recorded and released, you need to get the 4-disc boxed set that came out a few years ago, plus the 2-CD "Special Edition" ones.

However, if you just want the best (IMO) ones to get without getting "everything," go with the ones that were released when the Special Editions" came out in 1997.

Andy is right, both 2-cd sets contain the exact same music. The cheaper sets that come in the jewel cases don't have more music they just have more tracks. For some reason they just divided the music up more, for example: track 2 on the more expensive (also called slimline) release is called MAIN TITLE/REBEL BLOCKADE RUNNER. While the less expensive (jewel case) release divided the two cues into two tracks, track 2 is MAIN TITLE and track 3 is REBEL BLOCKADE RUNNER.

Another difference besides the obvious packaging difference is the face of the CDs. The more expensive (slimline) release has really cool laser etched images on the face of the cd, while the less expensive release has the usual painted on images.

I have both releases. I originally bought the slimline release but later bought the less expensive release also because I got a great deal from columbia house on them. Now I am keeping the cooler looking laser etched CDs put away in case I ever damage or lose one of the other disks. Like Sartori said you might not be able to find the slimline release any more, they didn't make as many. But the important thing is that you buy one of the releases of this excellent music, it doesn't matter which release, if you are a Star Wars music or John Williams fan this is a must have.