These are the most useful on my bookshelves in English, but they are out-dated because they don't deal with the establishment of our Senedd as the nucleus of independence:
John Davies: A History of Wales (Penguin 1993). Sort of standard, but playing it safe with the English Establishment and a bit full of place-names.
Gwyn A. Williams: When was Wales? (Penguin 1985). This is about the best I know of. An able historiasn who can think for himself.
On the literary front, I suppose we're stuck with T, Parry'a 'A History of Welsh Literature' (Clarendon Press, 1955, trans H. Idris Bell), but I don't reckon it much: it's very out-dated, and the translations are all 'poetical' thees and thous. That's true for Lady Charlotte Guest's Mabinogion too. The best in that line I have to hand - on Kindle - is Patrick E. Ford: The Mabinogi and Other Mediaeval Welsh Tales.
The problem is that the good stuff is in our language, and the English are not interested in us natives! There are complex reasons for this dating back to their early desire to please German-speaking mercenaries who took over the east. I can be quite boring about that.
Incidentally, I got the parentage of the original Dylan wrong - he was the son of Aranrhod, sister of the animal couple I mentioned, whose original fortress was the Milky Way, Caer Aranrhod, but in the story has shrunk to a place in Gwydedd. Another of her sons might be of indirect interest to you: for reasons I won't get into she swore he should have no name, never bear arms or marry any woman born of any people on earth. Her brother Gwydion tricks her into naming the boy Lleu Llaw Gyffes and into arming him, and eventually the High God figure, Math, helps Gwydion create a wife for him out of flowers. She is Blodeuedd. Unfortunately she doesn't really fancy him, takes a lover and has that man try to kill him. The reason you might be interested is that she ends the story changed into the Owl!