This is about the wizards who guard the gates of the worlds. These gates appear at crossroads and underneath railway stations - Grand Central in New York, and the Underground in London. (This may explain something about metropolitan railway systems....) The twist is that the wizards are cats. Real cats who get furballs, and fleas, and mess with string. Oh, and do the cute-kitty thing so that deli-owners give them pastrami. It isn't a sentimental book, though most of the people I recommend it to do like cats. It is fun, very well written, with a great collection of feline metaphors - "as irritating as the last flea in your ear which your claw can't quite reach". Aside from the cat-stuff, it is a light and entertaining fantasy-adventure, which presents its protagonists with some serious moral dilemmas. If you like any one of: Pratchett, cats or fantasy you'll enjoy this.