First of all, this book has more pages than listed on GR, 141 with endnotes.
Secondly, author Cole does a fine job bringing to the reader various elements of Celtic spirituality and tieing them to the season of Advent. Each day's entry is 2-3 pp, with a few paragraphs of commentary followed by a reflection, scripture, and then a prayer. As is the case for most modern prayer writers, these are a bit 'sappy,' for lack of a better word. They make me cringe a bit.
Nevertheless, this is still a fine book to mark Advent. One place where Cole is lacking is the same from his book on Celtic Prayers and Practices, and that is his lack of awareness or just plain disregard of the links between the Celtic Church and what is now the Eastern Orthodox Church. The most glaring example in this book is the simple fact that is starts on November 15, which Cole states was when the season of Advent (he doesn't give us a Celtic name for this season, just that it was known as the 'lesser Lent'), was observed in the ancient churches in Britain and Ireland. He fails to mention that this was the norm for all Christendom at the time, and that it is still the pre-Christmas penitential season observed by the Orthodox. In fact, he doesn't really detail why Advent was seen as a lenten period. He rightfully describes and organizes the book around the three 'comings' of the Incarnation, but more on the fasting (which I believe he ignores) and confessional aspect of the season.
Another place is that he doesn't tie the Celtic Church into the wider Christian world of the day. I recognize that is not the theme or purpose of the book, but aside from a passing mention of Celtic missionary work in Europe and maybe (can't remember now) the early Desert Monks who inspired all Christian monasticism, there is little to give the reader any indication that Christianity existed anywhere else in the world.
These small criticisms are not to say this book is without value. I enjoyed it quite a bit and have already bought his books for Celtic Lent and The Celtic Year. These are nice editions published by a British Bible society and worthy additions to any person's library.