Hold up here...
there can be a limitation on greater dispel magic that is GM justifiably:
Quote:
This spell functions like dispel magic, except that it can end more than one spell on **a** target and it can be used to target multiple creatures.
In essence, this is saying that it responds as if it were dispel magic, lesser, but that it targets more than one thing - which is all well and good and to that part of the argument, you are all correct in that it would affect multiple targets all at once.
HOWEVER....
The ruling would need to be based on the following question:
Is the book considered 1 item... or is the book considered multiple items (i.e. multiple pages)? In that instance, its effect would be determined through GM discretion. The GM could rule that the "book" is one item - a single book - and not to be considered as separate pages within a single book (or single object). Yet if you were to hand over a bunch of scrolls or parchments, they would, and should be counted as individual items without question of course.
Quote:
Area Dispel: When greater dispel magic is used in this way, the spell affects everything within a 20-foot-radius burst. Roll one dispel check and apply that check to each creature in the area, as if targeted by dispel magic. For each object within the area that is the target of one or more spells, apply the dispel check as with creatures.
Thus I feel that in book form - yes, it could potentially count as a single item with the result of a single explosion... but in parchment form, it would be counted as multiples as if you had multiple letters in your hand as if you were a postal worker about to become shredded postal worker soup. If you stacked the runes though on a single parchment, according to how this is worded, it would only activate once.
I think that's the key to utilizing GM discretion in this instance. Personally, I would say the book is a single item, despite the fact that I believe in cellular biology where we are billions of individual cells that make up the person, not a person made up of billions of cells. I know that sounds quirky to switch, but I can quickly see this type of thing being exploited on a regular basis.
On the other hand, if a GM still had an issue with this, they could opt to house rule that you can't auto dispel your own spells which would make the attempt to try this trick obsolete by the fact that you would more than likely (unless rolling a true failure of a 1) dispel your own stuff based upon your skill level as a caster in spellcraft. By the time you get greater dispel, your spellcraft should be something like 15 or 18 anyways.... so you would be rolling against an 18 to dispel which would mean you are likely going to succeed nearly every time.
Another way to bypass the situation is to also house rule that explosive runes by the same caster, in proximity, would harmonically resonate to the point of explosion if within a certain distance of each other - say 6" or less. Thus, you couldn't get away with stacking this up in a book, nor give out multiple parchments. I think that also would work for a viable control method by flavoring it as some kind of "time cop" situation where "two identical things can't occupy the same space at the same time" sorta deal because the magical energies would be competing and would "somehow" counter react with each other and explode. It's an idea for those that want to control this kind of thing.
Furthermore, I appreciate the comments on this thread, but please - there is no need to get all up in everyone's grill about how they perceive or play. I want to keep this a friendly discussion - not a hate fest on one person or another. Reading and responding to text online is not as eloquent in speaking and you often miss tone or inflection and it is easy to take words and phrases out of context or imply anger or other such things where it isn't necessarily due.