Real Absinthe (from Europe) tastes very strongly like black licorice. It is made with wormwood, anise, and other ingredients. It is usually high in alcohol content 100 proof or higher. The reason it is illegal in this country is that it contains a substance called Thujone which has similar chemical properties to the active ingredient in marijuana. She Devil is right about one thing...it is certainly an acquired taste, and not for the faint of heart. Some people died from Absinthe poisoning because 100 yrs ago there were no safety standards for distilleries and so many places aged their Absinthe in lead casks...hence lead poisoning. As for that green fairy stuff, what you must remember is that the original recipes used during the times of Poe and van Gogh have been lost due to the absinthe ban that went on in France. So the quality distilleries have tried their best to replicate it but now there are regulations on the amount of thujone that can be contained in Absinthe.
If you really are determined to try it, be aware that you will have to pay big time shipping and customs costs and there is no guarantee it won't get stopped at customs. Mine got in because the merchant was savvy enough to label it as flavored cooking oil. Since the label was in French i guess they never bothered to really examine it. The best advice i can give is to avoid the homemade stuff and go with a reputable label...i would recommed Francois Guy. Just know that yer gonna pay around $80 when all is said and done
Hope this helps you a bit.