Street Magic is the magic system update/compilation for Shadowrun 4th edition. As a fan of Shadowrun for 15 years now, I have to say this is not the best effort I've ever seen put out for one of role-playing's most original, in-depth settings.
While having access to 4th ed. rules for all the nice crunchy bits the good folks behind Shadowrun have come up with in the preceding years is good, I was honestly expecting more; more backstory, more mystical advancements, more supernatural challenges. These updates to the magic rules could have been printed in a booklet format. There are no new revelations about the world of magic in Shadowrun, and that's a big disappointment.
That being said, if you plan to play a magic-rich game of Shadowrun, this book is still worth the nuyen. At the least, it'll give you the tools to make new players go, "But that kind of magic wasn't in the book!" To any of Catalyst Game Lab's folks who might read this:
SOTA effects everything, chummers, even magic.