It all depends on what kind of shark and how it's prepared but most of what I've had tasted like low grade swordfish. In fact, if you see "swordfish" on sale for a very low price, make sure to ask specifically if that's really what it is. Wouldn't be the first time somebody tried to palm off mako shark as swordfish. I've seen that a couple of times.
It's delicious! It tastes like sort of a fish version of chicken, and is probably one of the best tasting fishes I've ever eaten. It's great with tartar sauce, lemon, and the like. Try it--you'll like it! WARNING: It's probably best that you let someone else catch and kill the shark for you. Sharks are a tad ill-tempered.