Here are links to the some of the GemStone/S 64 (version 2.2) documentation:

• Programming Guide (pdf)
• Topaz Programming Environment (pdf)
• System Administration Guide (pdf)
• 2.2.4 Release Notes (pdf)
• 2.2.5 Release Notes (pdf)

For an overview of some of the differences between Squeak and GemStone see The Terse Guide to GemStone.