Capes exploded in 2009. I personally think they are an essential item. As mentioned at the end of last week, I sleep purchased a cape which magically apparated into my wardrobe.
There are many types of cape (a jacket that fits like a shrug, often incorporating a batwing sleeve). I recommend you try before you buy to get the right fit. When I first put on my *JUNK* cape, I wondered if the one size fit all approach was a mistake – It felt 10 sizes too big!!
The style advice related to How To wear a cape is so varied and contradictory. Given that it is a loose fitting jacket, if you want it to drape, creating a beautiful feminine silhouette, you should wear it over tight fitted jeans, leggings, shirts and dresses, with heels. However, because it is loose fitting, you can get away with wearing it over looser clothes as well as layers without looking like a balloon.
Vertically challenged people beware – I wear my cape with boots, but this look makes you appear shorter. Heels are height magic.