In their introduction, the authors compare this work to the Raven and Kirk collection of reports on the Presocratic philosophers. In many ways, this is a very accurate comparison. Long and Sedley present a great collection of reports on the Hellenistic philosophers, many of whom (most of whom) do not have any surviving first hand accounts of their lives and doctrines.
Chapters are divided into schools, and subdivided into topics (ethics, logic, etc.). After each subdivision, the authors offer insightful analysis of the doxographical material that aids the reader's understanding of context, and usually works to put the various (sometimes divergent) reports together.
One important distinction between Raven and Kirk is the accessibility of this collection. Long and Sedley have separated the English translations in a separate volume, and placed the original Latin and Greek sources in a second volume. This makes the work less intimidating.
There were a few awkward cuts and organizations, but nothing to make this any less than a top-notch piece of scholarship. It was much better than Hackett's 'Hellenistic Philosophy'.