The reason for the title is that this is almost irish arrangement by numbers. There are plenty of varied tunes, airs to reels to jigs etc, but there is a sort of plodding-ness to it all. Some work better than others. On the whole I would recommend another book entirely - Mel Bays Complete Celtic Guitar, but this one works well enough. The tunes are not really difficult, and it would be a good book for a beginner trying to get to intermediate level.
Perhaps Mr Weiser has left the reader with the option of providing grace notes, and other ornamentations which make the Celtic Style so unique, because there's not much here.