When GOG releases some of these retro-games like the Ultima series, they often add many extras that weren't included in the original releases.

For instance, Ultima I comes with a clue books, 3 maps, and 3 manuals, and a spellbook. I could be wrong, but I remember the original only had a simple cloth map, not 3 detailed maps. I'm sure the other Ultimas have similar types of goodies as well with extras added.

Can anyone tell me how to determine which of these are things you'd find in the box with the original release of the game and which might be called spoilers or extras that only GOG released recently?

Thank you.

You will find these two sites helpful for your research:

http://www.ultimacollectors.info/index.htm
http://www.mocagh.org/loadpage.php?getcompany=origin

I had no problem downloading and got the goodies too. Ultima I just played the intro credits and then displayed the castle ... eternal do loop, and no keyboard key interruptped it. Ultima 2 would not accept keyboard commands. Maybe DOSBox is not recognizing my keyboard? Ultima III, got sound with the title sequence and then got stuck when it asked to press the spacebar and nothing happened.

Were the clue books released by Origin Systems, or by GOG? :)

The cluebooks were by Origin.