It was written by Mickey Hart (of the Grateful Dead) and K.M. Kostyal and is titled "Songcatchers: In Search of the World's Music." Can anyone recommend or comment on this book?

I don't think that the book was ever published in the UK. I bought my copy "remaindered" in a bookshop in New Orleans in September 2003 - surprising when the publication date is given as June 1st 2003.
It is an interesting book; more popular than academic. It takes an eclectic look at collecting across a wide range of traditions, dipping more deeply into figures that seem to interest him. Grainger, for example, is dealt with in much greater detail than either Sharp or Lomax.
One of the book's strongest points is the really interesting photos that are found on nearly every one of the 160 pages. I spent at least as much time on the photos as I did on the text.

Hart's credentials show him to be much more than just a rock percussionist. Here's what part of the blurs on the dust jacket says about him -

A well-known spokesperson and advocate for the restoration and preservation of the world's aural treasures, Hart serves on the Board of Trustees of the American Folklife Center and on the National Recorded Sound Preservation Board at the Library of Congress. His lifelong fascination with rhythm and the history of percussion and music has been documented in three previous books: Drumming at the Edge of Magic; Planet Drum; and Spirit into Sound: The Magic of Music.