Let's make this short, because time you spend reading on could be time spent playing the game instead (unless you're sneakily reading this in the office, in which case getting out your DS for a session right now might not be so clever). The Phantom Hourglass is a fully-fledged Zelda game, ingeniously designed to run on the DS. Nine out of ten, rush out and buy it. Really, what on Earth are you waiting for?
OK. You probably want a few more details. Well, The Phantom Hourglass is actually that rarest of things in the Zelda universe: a proper sequel. Normally, there's no direct link between one Legend of Zelda and another. Our elfin hero, Link, begins each one as a simple boy and goes on to fulfil his mysterious destiny. Bar the repetition of narrative, visual and musical themes and the constant elements of the classic Zelda game design, nothing ties The Wind Waker to Ocarina of Time or The Twilight Princess to The Wind Waker.
The only real exception to this was Majora's Mask, a side-story to Ocarina of Time which continued on with the same hero and the same visual style. Well, The Phantom Hourglass has a similar relationship with the Wind Waker. It begins where the Wind Waker ended, with Link and Princess Zelda (in the guise of the Pirate Queen Tetra) abroad on the high seas, in search of adventure. Encountering a mysterious ghost ship, our heroine is spirited away, leaving Link washed up on a small island, and faced with the impossible task of saving her.
The graphic style also continues, with the Phantom Hourglass sporting a slightly downgraded version of The Wind Waker's beautiful 3D cel-shading - still one of the great high-points of deliberately non-realistic game graphics. It has the same stylised, big-eyed cartoon characters, the same exuberant swirls of smoke and mist and comes from the same school of creature design, with traditional Zelda favourites given a distinctly Disneyfied spin. It's a good match for the DS, partly because the cel-shading helps conceal the limitations of the hardware in terms of textures and polygon performance, and partly because someone made the smart decision to keep the camera set at a top-down isometric point of view. This makes the game feel a bit like "A Link to the Past" - no bad thing on a device with a relatively small screen and limited buttons - while the fact that it's still a 3D engine means it has the flexibility to handle the odd more cinematic scene.