Hi Kelly - I'm only on day 5 of CS but finding it really good, easy to follow and I'm not any more hungry than I'd normally be.
You replace 2 meals a day with a shake/soup/bar, have a protien based meal once a day with unlimited veg/salad and you can also have up to 3 low-carb snacks a day (say certain fruit, cheese, ham, tuna, veg, 1/2 bar etc). The book that comes with the CS starter pack lists all what you can and can't eat.
There are loads of meal replacement diets out there, such as Slim Fast, and they are all kinda similar, but as Lexi pointed out CS is much lower in carbs than most, so you will lose weight quicker.
Good luck if you decide to give it a try, the starter pack from Rowlands (instore or online and their the only seller in the UK of CS) gives you everything you need to get started, even a shaker! x