We had celeriac chips last night.
Cut the skin off the celeriac, and cut it into chip shapes. Put the chips into a baking tray (I line mine with greaseproof paper to make sure that they don't stick) and drizzle with a generous amount of olive oil. Salt and pepper, and then into a hot oven for about 40 minutes. Turn them half way through. Keep checking them till they're nicely browned.
They won't go crispy like potato chips would do, but they have a lovely texture and flavour.
Or, you can make celeriac dauphinoise or celeriac boulangère, using the same recipe you'd use for potatoes.
Another favourite is celeriac and leek mash. This time, after you've peeled it, cut the celeriac into chunks, and boil in salted water till soft - around 20-25 minutes. Drain in a colander, and let the celeriac steam dry for a few minutes.
While the celeriac is cooking/drying, cut a couple of leeks into chunks and pan-fry gently in butter, till soft. Then put the celeriac back into the pan you cooked it in, add the leeks and mash/purée, using a stick blender. This makes a lovely alternative topping for shepherd's or fish pie.