Cover Artwork
The books were originally published separately, with each of the second and third books containing a synopsis of the story so far... Prologue for Golden Apple Prologue for Leviathan
When eventually released as an omnibus edition those extra texts disappeared (and other edits may have happened, too).
Here's an interesting interview with the editor responsible for putting the three-in-one version out. [Accessed at RAWIllumination 23 Oct 2011]
Legendary editor Jim Frenkel: How I helped save ILLUMINATUS!
[Bogus: IMHO the editor's argument that keeping 3 volumes in print proved difficult, and the omnibus solution worked better, remains a half truth. I can't slip an 800 page volume in my back pocket.]
Dell editions
Ro Ro Ro editions
Omnibus Editions
