According to the author, Deryni Rising (1970) represents the first modern fantasy novel. In that year, her books established the genre. How well has it held up over the years? Pretty well, in my opinion, but not perfectly. Much of the reason for its solidity is that she avoided the excesses of her time, basing her text style on the other genre styles popular in their day.
In this story, King Bryan dies, leaving young Prince Kelson to ascend the throne. Secretly opposing him for the throne is a Deryni sorceress, who assassinated King Bryan, and plans to tear apart his legacy as she seizes the throne.
For a first novel, the book holds together pretty well, although its plot's as thin as a made-for-TV movie. That comparison is not without merit. Not only could I follow the visual cuts, the chapters fell where the commercial breaks should go, complete with strong act-outs and mid-chapter twists. However, I found the constant one-sidedness hammering on the protagonists a bit much by halfway through. While I can believe that smart people can be fooled with misdirection, when this happens every few chapters, with people attempting to arrest and execute the most trusted servant of the prince, the whole setup stretched beyond credulity.
The prose is clear and serviceable, rarely leaving the reader to doubt who is thinking what at any particular time. Every character has a clear motivation. The plot moves along, rarely bogging down. There's a few info dumps, but they don't rise to any measurable inconvenience.
I can happily recommend the book, even now. I can't think of another setting quite like this one. It's like a mini Game of Thrones three decades before Game of Thrones was written, just a whole lot less murderous and far more family friendly.