The Holy Wells of Ireland
I've read a couple of books by the same author before now and those are well worth taking a look at –one called Irish Folk Medicine, and the other called The Old Gods: The Truth about Irish Fairies. Logan is a great author and a medical doctor by profession, so in both this book and the Irish Folk Medicine volume he has a lot of expertise to draw on when it comes to the folklore of healing.
The Holy Wells of Ireland isn't a hefty tome but I think it's fair to say that it covers all of the basics – the typical locations that wells can be grouped under (on the seashore, mountain or hilltop, bogs, churches, and wells that move), legends associated with them, pilgrimages and rituals associated with them, and the kind of purpose they're used for, the kinds of offerings that might be left, and the kinds of trees or animals associated with them, too. These are all dealt with in their own chapter, so it's well-laid out and the repetition is kept to a minimum – always a plus if you just want to pick at it for research.
It should be said that while detailed descriptions of some of the rituals associated with certain wells are given – the timing, the number of rounds made, walking barefoot or on the knees, the kind of offerings left, and so on – you won't find much in the way of details about the liturgy used in the rituals. If that's what you're hoping for you'll be disappointed, I'm afraid, but that's because it's basically all thoroughly Catholic. An outline is given – the number of stations or decades that should be done, the point at which the Creed is recited, etc. – and I have to admit, not being raised Catholic I only had a vague idea of what these mean (until I asked my husband). Although Logan is quick to point out where there are appearances of pre-Christian elements, and how it can sit uncomfortably in the Christian landscape, that's about as much as you're going to find.
This book is a good introduction to the subject, but it's not as in-depth as it could be, which is a plus and a minus. It's not too dense, but sometimes it's a little superficial in its coverage in places. In particular, although the seasonal pilgrimages to holy wells at times like Lúnasa are talked about, I think it would have been better to have added a little more context to the timing of the visit and how it fits into the traditional calendar, and so on. I would expect that most people who would read a book like this would already have an idea of that kind of thing so it's maybe not such a big deal, but having a bit more meat would have given a more thorough discussion of the subject, perhaps. Having said that, I think it's also fair to say that presenting the seasonal visits in the context of a wider practice associated with holy wells is also useful, and sometimes over-looked. The special occasions they were visited may have been when they were considered to be at their most powerful, but that doesn't mean they weren't considered to be useless at other times.
Although (as with his other works) there aren't exhaustive footnotes and citations, he does at least give passing references throughout the book, and there's a bibliography too. Many of the sources he draws on are now easily found online, at places like archive.org, so the book is going to be very useful if you're wanting to dig a little deeper and that helps to make up for any areas that aren't as detailed as you might like. Also useful is the fact that Logan discusses the context of his sources, and makes the point that although many of the sources are disapproving of the rites and rituals they describe, the more "hostile witnesses" often go into more detail than someone who is more sympathetic. In that respect, sympathetic witnesses may have had a tendency to gloss over the more uncomfortable "pagan" elements of practice and give less detail, while the hostile witnesses were more willing to emphasise them in order to underscore their bias and feelings about it. The latter is often more useful to us, even if the writer might over-emphasise or even embellish at times, or just spend a lot of time disapproving about stuff rather than getting on with it, but it's ultimately up to the reader to assess this kind of thing. This is a very useful point to make, and when referring to a source Logan makes clear whether or not he thinks the writer is hostile, which helps the reader interpret the information being given.
In terms of its "usefulness" as far as providing inspiration for practice might go, I think this is a good supplement but not so much a must-have for the bookshelf unless you're particularly interest in healing as a speciality. I can see myself referring to it every now and then, and it's a damn sight more convenient than trawling through archive.org to find the right antiquarian book or article (and it gives an idea of things that have survived to the modern day, and things that haven't, which the older sources obviously can't tell you), but all in all it's never going to be as well-thumbed as my favourites.
Even if it's not essential, there's some interesting stuff here, especially in relation to the instances of fish (usually trout, usually considered to be immortal or A Very Bad Sign if they die) that are found in some of the wells. This offers some food for thought as far as cosmology goes (the well of Segais, for instance), and the chapter on trees associated with wells will surely be of interest to quite a few folks as well. I would definitely recommend it as an easy and engaging read if this is your kind of thing. It's maybe one for the bookshelf when your book budget has snapped up the more essential items on your reading list, but it's worth a look at some point and it's cheap to buy second-hand. That's always a plus.