I've read them, they're actually pretty good! They do lean into the Christianity at some points but they aren't as egregious as most Christian lit. The author balances it well with Celtic druid beliefs and I don't remember them being too over the top religious (I haven't read the whole series in a long time but I did reread Taliesin last year).

Taliesin was probably my fave of the series, it has a lot of interesting detail on Celtic life, druidism and also has an interesting beginning storyline set in Atlantis. I enjoyed it, and the Christian stuff only comes up towards the end and is fairly easy to skip if you want.

IMO, they're pretty average. There are better retellings of Arthurian fantasy, but there are also worse. I read them as a teenager in the 90s because they were one of the few series on the store's shelves, but I doubt I'd read them again with so much other and more accessible media available these days.

The only really interesting novel by Lawhead I've read was Byzantium, a story of Irish monks on a pilgrimage drawn into an extended series of adventures.