I got my copy today...and I lost it somewhere here in this mess I call an office. Oh, here it is, he said, after 15 minutes of searching.
As Bill Hudson said, the biggest addition is the CD, which contains excerpts of 267 songs, almost every song in the book. The clips include metadata, so your computer will tell you what you're listening to.
The book is more-or-less the same as the 1993 edition. The 1993 book is 288 pages, and the 2009 edition has 313 - including additional songs and an updated discography and bibliography.

The additional songs:

For Mumia
The Ocean's Rising
No Mas Violencia
Take It From Dr. King
English Is Cuh-ray-zee
Or Else! (One-a These Days)
Tzena, Tzena, Tzena, Tzena (3 pages, with great background information)
Didn't Ol' John
Arrange and Re-arrange
The Hammers are Bangin' Away
One Percent Phosphorus
Trouble at the Bottom
Alleluya
Over the Rainbow
The Odds-On Favorite (Long Story Terse)
Wonderful Friends
If This World Survives

Oh, and text layout and music typesetting was done by the inimitable John Roberts (in 1993). I didn't know he did that sort of stuff, but the layout of the book is wonderful. There's a very nice picture of John on page 241 of both editions - that photo alone is worth the price...

...well, maybe not. But there are lots of good photos in the book, along with good stories and good songs.

Here's a link to the Web Page for the Book (click).
-Joe-