One of the all-time classics of aquariological literature, for sure. I have three copies; sadly, the original one I bought somewhere around '68 or '69 was unceremoniously disposed of when it deteriorated into a loose pile of tattered papers after years of diligent thumbing-through. It was one of my favourite wishbooks when I was a kid.
If you like this one, you should keep your eyes peeled for a copy of the Illustrated Dictionary of Tropical Fishes by Hans Frey. Equally as charming as the Innes book, but with a very different, very European flavour. It is far more comprehensive, and includes a much greater variety of much more detailed info.