This is a massive memoire by one of Edison's "boys," that is, one of the elite experimenters that America's greatest inventor included at the center of his creative teams. Jehl is totally admiring of the man, indeed loves him as a father and remains as awestruck as the day he met "the inventor of the phonograph."
At its best, the book makes the period come alive with personal details of Edison's greatest achievements and a sense of how he did what he did. (It was largely through outstanding teams, an uncanny sense of intuition in technological questions, and harder work than anyone dared imagine.) In addition, the reader gets to know the characters who worked in the Menlo Park facility, which was the prototype of all modern industrial research labs and phenomenally productive. You get technical details as well, which underline the achievements in all their complexity and audacity.
However, there is no doubt that this is an authorised version: Jehl wrote it as a living exhibit in the reconstructed Menlo lab that Henry Ford financed. As such, it is totally fawning over Edison and glosses over or entirely ignores anything unpleasant about him, which severely restricts its accuracy and usefulness to the casual reader. FOr a blanced view, the reader must seek the excellent bios that regularly appear.
This book is for scholars - a must as all the bios I know are based in large part on it - but also for history buffs and Edison lovers. (I read it for a writing project and found many details that I will use.) It is also splendidly written. Warmly recommended with these caveats in mind.