Borrowed this from library after being recommended by tutor and my dad. Absolutely loved it!!! Really well written to explain his theories and with loads of images to look at to back it all up and make it easier to understand.
Put very simply it is an explanation of how he believes that optical devices were used to support artists much earlier than we would think. He has so much evidence that I don't think of it as a theory but rather as fact. I came to it at exactly the right point as I have just been studying the 15th and 16th centuries and had been astounded by the seeminly amazing leap to incredibly realistic paintings of what look like 'real' people. I was prepared to believe in the change in materials from tempera to oil but it did still seem a bit strange. This explains how artists would have had access to devices which they could have used to very quickly get facial expressions notated on to paper. It makes it very clear that this isn't cheating and that the artists were still incredibly skilled.
I would recommend that any art students read this book as it was so enjoyable and interesting.