Ian Carr's MILES DAVIS: The Definitive Biography is one of the more meticulous lives of the great jazz innovator. Published first in 1982, it was thoroughly revised in 1998 to cover Miles' final years as well as shed greater light on his entire career.
A strong aspect of the book is Carr's access to various recordings which the average fan wouldn't have a chance to listen to, such as early projects in the 40s and concerts during the 1980s. Carr very thoroughly charts Miles' health problems and the horrendous squalor he was living in during the late 1970s, making the reader impressed that he held out as long as he did. The book is also well-researched, and Carr occasionally corrects mistakes made by other biographers, such as the claim that Miles recorded with Karlheinz Stockhausen (they never met). Carr knows the trumpet well and can speak on technical aspects of Miles' playing better than other commentators. One might also mention that the book is admirably typeset, and its ease on the eyes makes it a pleasure to read.
There are a few downsides to the work. Carr rarely attempts to show matters from the viewpoint of Miles' antagonists. His marriage to Cicely Tyson, for instance, is presented as if she was the one responsible for its demise. His coverage of the 80s too often is a dry counting of tour dates, and it would be nice to have some amusing anecdotes thrown in to allow the content to breathe. Also, the book holds no serious musicological analysis of Davis' work, although there are some superficial comments and some examples from various scores at the back of the book.
If you are looking for an overview of Miles' entire career that treats all of his phases fairly, from his early traditional jazz to fusion to the almost-pop of his 80s efforts, then Ian Carr's biography, in spite of its negative aspects, is probably the best available.