I received a 3L bottle of Angoves Classic Reserve 1999 Shiraz and was wondering if I could put it in my cellar to drink another year or should I drink it now? I've heard that you can only store certain wines which get better with time. True?

Depending on how it's been stored really depends on how long it will last.
A wine stored in optimal conditions will last for years.
You need constant low temperature (10-12 C), lack of light and vibration, as a starter.

Also the bigger the bottle the longer it will last, compared to a normal 750ml size.

All that being said this wine will be drinking fine now, but should last for a further 5 years easily, assuming the above points.