I don't know if this is typical of biographies written a century ago, but it's not like any biography I've read in the past 50 or so years in that it's less of a narrative about Bridger's life than it is a compilation of every known fact from every primary source that the writer, J. Cecil Alter, could find. Alter was a meteorologist who became interested in the history of the American West, primarily Utah, and would up becoming the editor of the Utah Historical Quarterly.
His biography of Jim Bridger isn't exactly a scintillating read; you don't get a lot of insights into Bridger's character other than what others wrote about him. But Bridger was such a fascinating character, perhaps the most foremost of the mountain men of the Old West, that the book manages to hold your interest in spite of Alter's writing style and methodology.
Readers who, like me, are fascinated by the American West will enjoy this book. Others should probably read something else.