The third book in Roger Zelazny's Chronicles of Amber series, things have turned for the stranger, with Corwin out to battle the forces of Chaos, his brother Random on the throne, and the siblings reluctantly working together.
There exists a Pattern, a mysterious and sinuously curved glowing thing on the floor of the basement of Amber's castle, which all of the blood of Amber must walk along to gain their powers. This walk is tremendously draining and difficult. In this book, Corwin discovers that the Pattern the royals have been walking is really only a copy and that a true, primal Pattern exists deeper in the fabric of the universe.
The intrigue continues as Corwin discovers hints that their father, King Oberon, may not actually be dead at all, as everyone had thought.
The next book in the series, The Hand of Oberon, proves just how true that is.