AppleTalk is loosely based on OSI (Open Systems Interconnect) a(n umbrella) protocol which promised much, but was used much only in Europe. You may find information on OSI easier to obtain, if you're looking.
Appletalk IS routable, but it's pretty nasty to configure on Cisco gear. It deals with network.node addresses. Notice when you go to the Chooser you only see the local Appletalk devices. You can manually enter an IP address in the Chooser and mount remote servers, but that's not using Appletalk, it's using IP.
Appletalk is dead for everything except printing. I've killed it at work except for our laserwriter 8500's. We're all IP and it's MUCH easier and faster. Here's a link for more Appletalk info:
Appletalk was one of the first networking protocols, and for it's time was really revolutionary. It worked over multiple interfaces and was light years ahead of netbui. Unfortunately it's chattiness gave Novell and Microsoft geeks a reason to ban in on LAN's, although that was more political than practical. Apple has replaced Appletalk with TCP/IP for everything. There is no reason to use Appletalk anymore, and Apple only added it to OS X when people bitched they couldn't use their appletalk printers. If you're using OS 9 or later and mount an Appleshare volume, it tries to use IP to mount it first, then falls back to Appletalk.
I wouldn't say that it is nasty to configure, you need to configure
appletalk routing eigrp <router id>
appletalk cable-range N-N H.H (where N is cable range start-end, and H.H is suggested address)
appletalk zone <zone 1>
appletalk zone <zone 2>
appletalk zone <zone 3>
... (add as many zones as you want)
Not that hard to configure. It is fully routable across an Enterprise network, but there is no way that a service provider (ISP) is going to route your Appletalk to anyone else. You can use L2TP (layer 2 tunnelling protocol) to connect two subnets across the public Internet, and allow appletalk connectivity between them.
The big question is, why would you want to run appletalk. I can't wait until I can turn it off, the only thing holding us back is supporting legacy printing with old Mac OS. IP is the way to go.