Hi U2, I use styrene every day and can vouch fully for what Joe is saying. I use Plastic weld to stick styrene together but liquid poly is also good and has a nice smell:O)
Evergreen and Plastruct are the premier strip manufacturers with the former making the better strip, and the latter making the better rod, it being round and always solid.
All good model shops should sell a range of styrene sheet, usually in A4 size or very similar, and the really good ones selling larger sheets that are good for decks etc.
10thou (.25mm) is good for representing plates and for laminating curves, and also good for flanges etc.
20 thou (.5mm) is good for the above on large scale models and also has some strength for making some structures where the edges can be seen, though you can chamfer the edge of thicker plastic down to recreate a thinner wall.
30 and 40 thou (.75mm and 1mm respectively) are good for structures such as deck houses.
60 thou (1.5mm is good structural material, but I would be careful using it on superstructures where balance is more critical.
You can get 2mm, 2.5mm and even thicker on occasion and these are probably best left unless you need to laminate a block of plastic to carve.
It can be cut, sawed, drilled and carved, it can also be heat formed with care using a soldering iron for rod and strip, and in sheet form using hot water or a hot air gun. The oldest trick in the latter's book is stretched sprue for making aerials on tank models where you heat some model kit sprue over a candle/naked flame and stretch the sprue into filament when the middle softens but this is a smelly and dirty job.
Look at the shapes that Joe and other modellers make with styrene on their models and you can see how versatile it is:O)