Just because one person passed after having rwad it does not mean it is worth the money. Noone I know who got through OASC (and I know more than a few...) did it by buying revision hints.
There is nothing out there worth buying in terms of hints, tips or advice. All you need and more is available for free in hundreds of places, you just have to be bothered enough to pull out your finger and find it.
If you can't do that, then you shouldn't be applying.