I'm sure many of you are going "What is this? I've never heard of this?" But fear not, for I shall tell you the tale as I understand it. Way back in 1991, Ghost in the Shell 2 began its circulation in Kodansha's Young Magazine and came out in slow installments up into 1996. All well and good, everyone's got their fix of continued Shirow goodness, and now fans to wait for a collected volume of the story.
Time goes by, a limited edition Solid Box Set is announced as the premiere of the collected GitS 2 and serving as the ultimate Ghost in the Shell package, containing both volumes of GitS in hardcover and a slew of other goods. Piles upon piles of Preorders were made and then the release day hit and the boxes were nowhere to be seen, much to everyone's dismay(see the MS Hyperpages for the firsthand account of one such fan).
Eventually the box did come out and everyone was happy, but puzzled. What they saw in the collected GitS 2 was not the same as from Kodansha's earlier run. In fact, it was a completely different story, all new art(tons of it computer generated and in full color, no less), and not a trace of the original to be found anywhere. This new GitS 2 became the standard GitS 2 in subsequent releases(with a 24-page epilogue tagged on and a rather explict scene taken out preemptively by Shirow for the mass market release), and what came before was basically forgotten.
Then in the middle of 2003, seemingly out of nowhere, GitS 1.5: Human Error Processor was announced, fans that missed the magazine run would finally be able to see the original version of GitS 2. In addition to collecting the story in a nice little hardcover book, they included a CD-ROM with an 'enhanced' version of the book, basically a big Flash runthrough of the entire thing, with sound effects added in. They also included a screensaver that seems to go through mainly the cover art for the different parts of the volume, nice to look at, but I'm not a fan of the Flash-based screensavers.
Originally there were 4 parts(Fat Cat, Drive Slave, Mines of Mind, and Lost Past), with each part split over 2 issues. It was mostly black and white illustrations with just a smattering of color pages at the start of each part. The story continues following Section 9 and their covert ops investigations. Unfortunately beyond that I'm at something of a loss, as it hasn't been translated into English yet and I can't read Japanese. As an aside, I suspect the naming of the collection to be a joke about how this didn't end up being the 'real' GitS 2, but just a big mistake by Shirow.
The upcoming "Ghost in the Shell 1.5" CDROM, on sale July 23rd on sale for 2,381 yen will include four episodes of the Ghost in the Shell manga that were never published in the Tankoubon.
The four episodes are Fat Cat ('91), Drive Slave ('92), Mines of Mind ('95), and Lost Past ('96). Also included will be a 184 page booklet.
Masamune stated, "In GitS 1 I didn't depict how the members of Section 9 usually are, but to tell the truth I had more than 20 rough plots for depicting that. Some of them were published in a magazine, but the other stories were never fleshed out since GitS 2 focusss on Motoko.
"I'm happy that they will appear again because I was afraid it would be a while before they would be published. Thank you, my editor and others. I have to admit they are rough, but I like the atmosphere."
Final thing to share with this is an interview about GitS 1.5 with Shirow. Unfortunately it's Japanese only, but I'm sure some of you are able to read it, and there's some more images in the article as well.