You can now download Katherine Kurtz's Deryni Rising, the very first Deryni novel, for only 1.99$ here.
Here's the blurb:
In the kingdom of Gwynedd, the mysterious forces of magic and the superior power of the Church combine to challenge the rule of young Kelson. Now the fate of the Deryni -- a quasi-mortal race of sorcerers -- and, indeed, the fate of all the Eleven Kingdoms, rests on Kelson's ability to quash the rebellion by any means necessary . . . including the proscribed use of magic!