Well, I am also biased (having written IA Magick along with some forthcoming works) but will add that I wrote the Magick book based on lot of real world occult practices of the era but also wanted to have a system that could model magic as we see it in various types of fiction set in the Victorian Era. Thus you can run a fairly low magic occult game closely resembeling the real world, a very Lovecraftian game where the supernatural is fairly prevalent and dangerous, or even a high-magic game with a fey Victoria and Unseelie spies from the Continent. Just about anything you can think of really. I think its very adaptable and I am quite pleased with it.
Since they have been mentioned already on these boards by either Gareth or Walt I can also say that I have written a Grimoire, focusing mainly on incantations but also with some other spells appropriate for the era, and a Faeries book, which much like Magick can be used to run a wide variety of different styles of games.
