Except the history of earliest phase of Islam, this is a great book to read as an introduction to Islamic history. Its short and well written as all books by Karen Armstrong are. At one place she states that ‘the claim that Prophet Muhammad had been the last and greatest of the prophets is not made explicitly in the Quran’ . But if you see 33:40 of Quran it is stated that Muhammad PBUH is the seal of the prophets. Apart from this and some other mistaken details , this book is worth reading.
P.S.
The best book on beginning of Islam as a biography of Prophet Muhammad PBUH is that by Allama Shibli Nomani and his student Syed Suleiman Nadwi. For anyone reading the biography of Prophet Muhammad PBUH for the first time, it is highly recommended that it should be read. The author clearly indicates why western historians and biographers make mistakes in recording the life of the prophet. One wonderful example is how the writer has proved that the Battle of Badr was a defensive act by Muslims. It is a 7 volume text in Urdu and I luckily bought all volumes for 1200 rupees from new Darrussalaam shop at University Road Karachi.
Sights Insights 
I have read Karen Armstrong’s “Islam: A Short History” and would thus like to recommend a much Better and Fabulous book on the History of Islam particularly on the life of Prophet Muhammad(PBUH)……..it is “Muhammad(PBUH) by Martin Lings(Abu Bakr Siraj Ad-Din)”
he is an award winner for this Beautiful, Flawless book…..and has undoubtedly presented Islamic history unlike by any Western Writer!!
Its a MUST Read.
Furthermore i do agree that Karen Armstrong’s Book has some flaws which does not make it as good as Martin Lings!!
P.S. Apart from this I must second you by endorsing that the book by Syed Sulieman Nadvi and his Teacher Shibli Nomani remain as an authority on the Life of Prophet Muhammad (PBUH) and will remain so in the times to come!
yes right, Martin Lings’ book is great too. I was reading it but then I started Shibli’s and left Lings’.
Well, Lings writes directly based on the early Islamic sources. Armstrong is writing as a historian that uses other sources, non Muslim ones included, and is being critical of the supposed “miracles”. Just a different perspective, I suppose.
yes right. but good thing is Armstrong is not so critical (people often think her to be a pro-Islamic) as others are, as far as I know.