Is the book titled "Towards a relative chronology of ancient and medieval Celtic sound change" by Kim McCone the same as "Progress in medieval Irish Studies"?

Please do help me if you have but the faintest clue what I'm talking about! I'm presently very pissed and nobody seems to give a flying f*** about my situation.

Here is why I'm asking and why I'm so pissed off. Ok first, I ordered from amazon the book called "Towards a relative chronology of ancient and medieval Celtic sound change" by Kim McCone. However to my great displeasure was sent instead "Progress in Medieval Irish studies" and was later told by the seller that these two books were one and the same. To my astonishement both have indeed been published under the same ISBN. They nevertheless appear to be in reality very different in content. So what's with this? Are they really the same? Please help, I looked on Internet and asked around and nobody seems to be able to help me.

Go raibh míle maith agaibh!!!

I've no idea.

But the author might!

From NUI Maynooth website

Head of Subject

Professor Kim McCone,
Contact: 00+353-1-708 3710
Email:

ISBNs should be unique. Even if the work is revised very little, it needs a new ISBN. Really the content should be the same if the ISBN is the same.

From here:

http://www.digitalmedievalist.com/bibs/irishlit.html

McCone, Kim. Progress in Medieval Irish Studies. Maynooth: An Sagart, 1996. ISBN 0901519359.

And from here

http://openlibrary.org/books/OL620854M/Towards_a_relative_chronology_of_ancient_ and_medieval_Celtic_sound_change

ISBN 10 0901519405

These are not the same ISBN.

So what's going on here?

Here is the publishers website:
http://www.ansagart.ie/

Thanks Seánw and Aonghus.

Turns out Aonghus that the author's email address that you gave me was pretty helpful. I wrote to him and he told me that there was indeed a mixe up in the ISBNs of the books. 'Progress' was by mistake given the same ISBN as a 'Relative Chronology'. When this was noticed, a new ISBN was made but the book at that point was already in print. They then decided to print out stickers with the new ISBN in order to place them on 'Progress'. Nevertheless some copies without the stickers managed to make their way on to the market which explains why the two books are being confused.

Sheesh!