It is bitter and taste of iron. Kids hate it and lots of adults don't like it.
As a side veg: Tear/cut the leaves off the stalks and boil for 10-12. Drain and put back into hot pan, add knob of butter for flavour, mix well and serve.
In stuff: De-stalk, finely chop and add to stir-fry, curry, or pasta sauce. Needs at least 5 mins.
Snack: De-stalk, cut into crisp size, spread on baking tray, use spray oil (flora one cal or similar), add salt/pepper/chilli powder/other flavours to your taste, then bake for five mins at 180c, toss occasionally and keep an eye on them, they burn in the blink of an eye. This is your best chance to get kids to eat it.