This is a review of the Nestle-Aland Novum Testamentum Graece, editione vicesima septima revisa (revised twenty-seventh edition), edited by B. and K. Aland, Karavidopoulos, Martini, and Metzger. The standard abbreviation for the work is NA27.
Other reviewers who know more Greek than I do have already dealt with the edition itself; here I only want to sort out a confusion of ISBN numbers.
NA27, in blue vinyl boards, without a dictionary, is ISBN 9783438051004. If you search for that ISBN on Amazon, you turn up an edition priced at $39.99. But Hendrickson Publishers has collaborated with the German Bible Society to release copies of their critical editions to the United States at lower prices; hence an Amazon search for ISBN 978-1598561722 leads to yet another product page for NA27 in blue vinyl boards without a dictionary, but this time priced at $25.05. Let me say it clearly: ISBN 9783438051004 and ISBN 9781598561722 refer to exactly the same volume: there is absolutely no difference between them whatsoever, except price. I know this because I ordered ISBN 9781598561722, the edition distributed by Hendrickson, and received an immaculate copy of NA27, which had ISBN 9783438051004 printed on it. Why Hendrickson created an ISBN which does not appear on the printed book, I don't know. I imagine because they wanted to distinguish the copies which they distribute from the copies which the Bible Societies distribute.
NA27 without dictionary distributed by American Bible Society: ISBN 9783438051004, $39.99.
NA27 without dictionary distributed by Hendrickson Publishers: ISBN 9781598561722, $25.05.
The price is the only difference; you get the same book.
Two other ISBNs deserve mention: ISBN 9783438051073 is NA27 with a German dictionary, and ISBN 9873438051158 is NA27 with an English dictionary. I believe Hendrickson distributes NA27 with the English dictionary as well, under a different ISBN and at a lower price, but I do not have the ISBN.