I have read Armageddon's Children, and enjoyed it immensly. When I was reading the Word/Void trilogy, I didn't really expect that the Word would lose. Even with the death of John Ross, the hope of humanity being able to avoid the demon wrought devastation was still there - in the form of Nest Freemark and her gypsy morph child.
But from the get go in Armageddon's Children you know that the Demon's have destroyed the world as we know it, and are just mopping up the survivors.
The hope of the gypsy morph (which is revealed to be Hawk) is that he will lead survivors to a better world (which we know will be what becomes the Four lands in the Shannara series).
However Armageddon's Children does have much more of a Word/Void flavour/feel, rather than that of a Shannara book.
Book two The Elves of Cintra is much more of a true blend, what with Knight of the Word, Elves, Demons of the Void, The king of the Silver river, human survivors of the Great Wars, and Elfstones all combined.
Apparantly Book three The Gypsy Morph will bring in an even more Shannara feel, and ends in what will be the period leading up to the First Druid Council of Galaphile.
However I have heard somewhere (maybe it was even the Terry Brooks offical website) that there will be another shannara prequel trilogy set between Gypsy Morph and the establishment of the Druid Order.