Ghost in the Shell (known domestically in Japan as Mobile Armed Riot Police) is a long running multimedia saga also written by author/artist Shirow Masamune. Starting proper in 1989, GITS began as a manga much like Appleseed, but quickly gained momentum and much greater popularity worldwide, appealing to a wide variety of audiences from garden variety otaku to the scientific and philosophical community.
Ultimately, the series has come to include at least three omnibus style manga compilations (roughly equivalent to about six or seven Appleseed-sized volumes), three motion pictures, two syndicated anime television series, and approximately four written novels.
Similarly to Appleseed, GITS uses police procedure as a plot basis, but goes much further and questions arguably deeper subject matter including (but not limited to) cloning, the artificial reproduction and duplication of human consciousness (a.k.a, the human "ghost"), sexual slavery, and mind control. For a more complete (but unfinished) look at the relations between Appleseed and GITS, have a look at the Comparison to Ghost in the Shell segment of our What is Appleseed? series. The most complete and accurate info, of course, will be found on the massive GITS Wiki, which we're proud to be a sister site of.