Hello, I’m currently looking into the development of various ‘strands’ of Christianity in Europe throughout the Dark Ages, and I seem to be struggling to find any books that aren’t pastoral calls for Christians today and not written by academics.
From my understanding, Early Celtic Christianity by Brendan Lehane is a good book, but are there any more? Thanks in advance!
It’s not specifically on Celtic Christianity, but Marc Morris’ The Anglo-Saxons has some good insights on competing strands of Christianity in Britain, and how that interweaves with political domination of the land. Morris is a historian, but the book is written for non-academics and is wonderfully readable.
Just as an FYI, you might have more luck researching Insular Christianity; Gaelic Christianity isn't really used anymore since it implies a kind of coherent and explicitly 'Irish' Church, rather than a loose confederation of broadly similar Churches distributed across the Early Medieval British Isles as a whole.
Wendy Richards' Wales in the Early Middle Ages and The Celtic Church is a good place to start.
I'd also suggest Hughes' The Church in Early Irish Society.
I'm currently reading The Flowering of Ireland by Katharine Scherman and I'm finding it a very very good overview of the spiritual history of Ireland. I can also recommend Living Between Worlds by Philip Sheldrake.
For more details on the belief system itself, Kenneth McIntosh's Water From An Ancient Well is a classic, as well as J. Philip Newell's Listening For the Heartbeat of God. Both of them are much more modern takes.
Hope that helps!