Not to sound trite and unimaginative, it's a wonderful book. Written in the best type of English, the top. It's not any product of Orientalism - far, far, far from it. I find it wonderful for various reasons.
The narrative. It's captivating, it again and again brings tears to eyes on which i have no control to resist. It compels one to cry out of love for Prophet, the Man of God, Mercy for two Worlds. One surrenders to the Truth owing to the prose. Although my mother tongue is Urdu, yet I have found no work in Urdu, a few best I've read, that match the quality of such a captivating and gripping prose.
The sources of the book. As the title clearly shows, it is based on the earliest Arabic biographies of Prophet, like, Ibn Ishaq, Ibn Hisham, Ibn Sa'd, books of Hadith, etc. - to name a few. Some portions of the Arabic sources have been translated for the first time. I was amazed to find out how much an ordinary Muslim in sub-continent knows about Prophet which an English Muslim may never know, were he to remain among English speaking people and not come in contact with Arabic, Persian or Urduu literature on Sirah.
The grace of the book. I felt the grace (barakah) of Allah while going through the pages, through the lovable small chapters (which make the reading more interesting and light on the part of an immature reader). Lings himself said that while writing this book he felt the presence of Prophet heavily.
Best biography in English. On the flip of the book is written this passage: this book was declared the best work on Sirah in the English at the national Sirah conference, Islamabad, 1983 and an award of $5000 was made to the author by the Government of Pakistan. When Shaykh Hamza Yusuf was looking for an English biography of Prophet for his students, he was dismayed not find great books. But his search was over when he found this books, and recommended it as the textbook biography.