As far as fantasy goes, each new fantasy title that is released is a shiny and promising volume. As such you really cannot judge the book by its cover, but have to delve into reading about the synopsis and reviews from others. What does it have? A strong magic system (like Brandon Sanderson)? Worldbuilding (like Tolkien)? Or strong characters? Whatever you want in the book you really need to hunt and work out if it has those. The Black Prism had a nice mix of appealing characters (if, like with Robert Jordan, a touch stereotypical at times - though the female characters were really well developed), great worldbuilding and a brilliant magic system.
The magic in The Black Prism focuses around the colour spectrum and is as much politically based as magically based. There are individuals with the ability to wield magic based on the colours of the light spectrum (generally only one or two colours at most) but this magic requires the individual to see that colour and so is limiting. Then you have the Prism, the one individual able to break light into all the colours. Only, as it turns out, using magic destroys the length of your life, turning you into a colour wight at the end unless you are freed by the Prism (basically he ritually kills you). So the Prism serves as a kind of religious and magical balance in this world and there is only meant to be one at a time.
Only, our story begins in a world fresh from having had two Prisms fight over who was the real Prism (which leads to some interesting twists, but ones which are roughly handled at points). And further, as it turns out, our Prism Gavin Guile, has a bastard son alive in the world along with several new enemies arising. So not only does he have the usual politics of the world to deal with, but a new set of problems which drive the plot.
It is the whole worldbuilding and political intrigue that drives this novel and makes it one of the better fantasy releases in the past few years. That said if you tire of epic fantasy as a genre it isn't particularly doing enough to ease your sense of tedium. That said, if you are a fantasy fan, look forward to reading this and make sure to get onto it because it is top notch epic fantasy storytelling.