One of the most informative, relevant, and fascinating books I've ever read. It was by no means an easy read. But for the amount of education you get out of it, the read is well worth it.
The author traces the history of monotheism (Judaism, Christianity, and Islam) and shows not only their interconnectedness, but also their literal unity. The detail in the exploration of the history of monotheism was indeed comprehensive - but also appropriate as it shows how religion has developed from era to era and how there is absolutely no universal truth or standard even within those sects. Instead they bend and change based on the needs of the people and those who have power over them.
It was a remarkably well-balanced and informative book that all religious people should read.
There are few among us that would pick up a book of Shakespeare and just start reading it for enjoyment - those 500year old writings are incredibly difficult for us to understand because the language and culture has changed since their writing, so we know you should look up some background or cliff notes or something to help us understand the ideas of context of what we read. And it's only all the more true with the religious books that are much older and have the added barrier of the translaters' bias and agendas - it is irresponsible to read old spiritual books without reading about the history, translation, and context of those books. Karen Armstrong does us all a favor by making a single volume that it is so useful for exactly that purpose.