Spelljammer was abandoned while incomplete. There are modules out there connecting some worlds, but not others. For example, there is Kryynspace, Greyspace, and Realmspace, and that's it.
It's too bad that this world was abandoned. I'm trying to get my hands on the rules or the boxed set, but all I find is the Spacefarer's Handbook, the last Spelljammer product published.
There are Spelljammer novels out there, but I would rather read some Sci-Fi books, like Douglass Addams' Hitchhiker's Guide to the Galaxy.
Other Spelljammer sites include: