Though perhaps a fitting reward for telemarketers who call during dinnertime, I don't recommend eating humans, but include them for completeness. They do end up on the dinner table now and then.
The biggest problem with eating human is that it's not sold in stores, so you first have to go out and kill one. Despite absence from the endangered species list, killing humans is dangerous and highly illegal under most circumstances. Then you have to clean and butcher the human yourself, a task for which most home kitchens are not well equipped. Finally, there are the difficult questions to answer when the police investigators arrive.
Beyond all this there are some very significant health considerations.
General & History
Eating humans, called "cannibalism", has generally been associated with religious ritual or extreme hunger. In either case, culinary considerations are rather secondary. False accusations of cannibalism have been common throughout history as a means of de-humanizing some population that was not liked or to justify exploiting or destroying that population. Even reports of ritual cannibalism by the Aztecs are highly questionable.
On the other hand, long pig is still on the menu in some places - though the dish is in decline. In New Guinea, Japanese troops during WWII followed local custom in eating roast Australian soldier. The last really notable person New Guinea natives ate was Michael Rockefeller (Smithsonian, March 2014) - they've mostly been converted to Christianity now, a religion that frowns on eating long pig, but does not forbid it (declared by the Pope in 1972, after the Andes plane crash).
There are occasional reports from Nigeria of eating humans, and in February, 2014, a hotel restaurant in Anambra state was closed by authorities for serving human. Two fresh heads were found, and 11 people were arrested (IBTimes, UK).
The only reasonably reliable report I know of as to taste and texture of human is that of New York Times reporter William Seabrook. He reported it was very much like veal, a little tougher, a little stringier and with a somewhat more mature flavor. His description sounds a lot like the new "free range" veal popular with the chef set, and that should be an acceptable substitute anywhere human is called for in a recipe. Others, though, say it's more like pork, and the structure of the meat is reported by scientists to be similar to that of pork, so take your pick.
Humans are essentially wild animals, not raised under the tightly controlled conditions typical of our industrialized agriculture. They are free to contract various diseases and many of these diseases are 100% transmittable to other humans who consume them.
Among these diseases are Trichinosis, Hepatitis and HIV (AIDS). Trichinosis is more widespread than most people realize because it is often asymptomatic, but AIDS is a much more serious risk. Many other more or less severe diseases and parasitic infections can be contracted.
Human should always be well cooked to an internal temperature of at least 165°F/70°C before consuming and brains should probably be avoided altogether (unless you are already a zombie).