I finally got the two CDs from ASA (Casebook and Rulebook). It's really handy to have the rules at your fingertips whenever a "what if" situation strikes you.
Though personally, I wish ASA would combine the casebook and rulebook again. When I first started in the early 90s, I seem to recall examples printed under the rules, which is basically what the casebook seems to be. I don't know if they separated them to improve the readability of the rulebook, or if they just wanted a few extra bucks from me. However, I think a good idea would be to put the casebook in the back of the rulebook after the rules supplements or the mechanics section.