You can't buy it in the shops, but the first (and last by the looks of it) true Oblivion expansion is available on Xbox Live for 2000 Microsoft Points (around £20). And while twenty-quid might seem a lot to ask for an Xbox Live download, what you're getting makes the ginormous massive RPG even ginormouser (yes, that big) by adding a whole new area to the world map to go and explore for around 30 hours.
If you're unfamiliar with Oblivion full stop, you'd do well to read the glowing 10/10 review, which will explain how the game plays and why you need it in your collection. This review just concentrates on the expansion, Shivering Isles.
The whole way you enter the new chapter could have been handled better though. Once you've installed the pack nothing happens to indicate your new purchase. The game loads in the new content when you fire up the original disc but that's it. There's no mention of Shivering Isles on any of the menus.
Instead, you have to wait about a day (in-game, thankfully) before a new quest pops up tipping you off about a door that's magically opened and is causing some headaches. It's then up to you to set it as your active quest, you could always ignore it and carry on about your business, but that would make downloading it a bit pointless.
Shivering Isles doesn't bring anything drastically new to the already-impressive world Bethesda has created, it just adds to it. There are new enemies to deal with, new NPC's with their own stories to tell and new items to seek out. You can go as deep as you like into spells, ingredients and quests, or just enjoy exploring the world and see what happens. The beauty of the original is retained every bit from the original game in the add-on.
You can jump right into SI even if you've never played the game before (you'll have to do the first dungeon-escaping mission though) or take your character with a zillion hours of experience straight there. The game tailors itself to your character's skill and experience. Don't worry if you're a n00b, you won't have to spend 900 hours playing the original before you're hard enough to cope with the Isles.
Once you've gone ahead and found the doorway to the Shivering Isles, a whole new story arch begins that's filled with quests and NPCs to locate, and extract information from. Your first job is to get through the Gates of Madness, guarded by 'the gatekeeper', who'll knock ten bells out of anyone trying to get near the doors. The key to the gate is stitched inside him meaning that you need to use your brain before your braun.
Between you and the Gates of Madness though is an area called The Fringe, designed as an enclosed area to test those who wish to travel further. Here you'll find the little town of Passwell and residents who'll provide you with clues to get past the gatekeeper. Once that task's completed you'll have a decision to make. The Gates of Madness comprise of two different doors and you have to choose which way to go; down the road of dementia or mania. Both lead to the castle of Shivering Isles ruler Lord Sheogorath, you ultimate destination, and true beginning of an epic adventure.
So begins the story of another tale in the ever-expanding Elder Scrolls universe. But just as before, you can take your time and explore the world filled with numerous camps, villages, ruins, castles, caves and other places of interest that'll keep you busy as well as the main quest.