I have a collection of books about Arthurian legend and have done since seeing Excalibur back in the day. This is one of my favorite series based on that legend. It remains my favorite of the series. The beauty of the legend is that it can be told in a myriad of ways with Arthur, Guinevere, Camelot, etc as the core. Here it's told with Atlantis being part of the mix.
I like that Merlin's story gets told, he's often in a strong background character in other books. He gets to tell his story here, not just as a magical being but as a warrior who can wield a strong sword.
He has frailties but his strength and wisdom outweigh them.
I had a bit of difficulty becoming accustomed to the narrator, but eventually did as the book went on.
I can absolutely recommend this book, series and author. If you enjoy Arthurian legend, it's a must. If you like a story well-told, it's a must.