I'm a big fan of John Matthews, and Caitlin as well... but I must say I enjoy the books from a spiritual viewpoint much more than a scholarly one. I'm not a scholar myself.. just one in training, but I can read between the lines.
I'm critical of the Matthews, because they tend to use some of the old texts to favor their points... and perhaps leave out what doesn't favor their points. It isn't all that bad though... still I tend to stick with books more like "Celtic Love" or "The Celtic Devotional" when reading the Matthews.
In this book, there really isn't much by Mr. Matthews. The introduction... yes. Thats pretty much it. The rest is a collection of essays on Celtic related studies. I spent the most time looking into the essays on the Ogham (which make up about 1/3 of the book).
Anyone who knows scholars knows MacAlister is full of it. This essay, on the Ogham, takes a prime seat in the book, but its little more than bunk. "Wishful thinking" is all I'll say about that.
It just seems to me that the John, the editor, chose a bunch of essays that reflect his view on things, ambiguous things at that, and then threw in a couple shorter essays for diversity.
Still, there are controversial opinions included in this work, and there is much to learn. I recommend this book, but only to those who have some knowledge in the area of Celtic studies, and even to them I say take this with a grain of salt, and don't let this be your only source of information. (Which I might say about any work on a topic so controversial this).
I was excited to get this book, because it was very well recommended. John and Caitlin Matthews reprint some historical essays that are hard to find, and write in a clear style. However, I thought it was too much dry history. I was forcing myself to get through it and not retaining what I read. This would be an excellent reference book, but not something I would plan on reading cover to cover.