You're either going to love this album or hate it, but if you do hate it, I'd almost be prepared to bet money that it will be due to one thing and one thing only: the authentic late mediaeval pronunciation. I myself love it, but even I have to admit that the pronunciation takes a little bit of getting used to, especially as I like Charles' normal accent very much.
One thing is not in doubt, however: even without the helpful sleeve insert, you will not mistake the words, despite the strange way they are enunciated. Charles' diction, always first-rate, is so utterly crystalline on this recording that you can actually hear the "w" in the word "wring"; that may possibly just be erring very slightly on the side of overdoing it, but frankly I'd rather have that than indistinctness, which is a fault in so many otherwise very good singers.
But if you can set aside any qualms you have about the pronunciation, this recording is unreservedly excellent. I think Charles picked the songs himself, and if so he's chosen some beauties; they run a whole gamut of emotions, and are without exception passionate. I think he particularly excels at anything that has to be sung with feeling, because he always puts it across with such utter conviction. Whether he is burning with unrequited love, blissful because that love is now suddenly requited, in the depths of misery because he has lost his love, or philosophical in the absence of his beloved, he has a wonderful ability to make you feel whatever is in the song. For me, he does that like no other singer, to the extent that while he is singing I am so captivated that I find it hard to recall what a cheerful and equable person he is in real life; all I can hear is the passionate, tormented soul pouring his heart out through my headphones. Now that's genius.
Verdict: I loved this the first time I heard it, but if you don't, play it again a few times till you get used to it. I think you will almost certainly be well rewarded.