AC
You can treat celeriac like a root vegetable but it has to be put in acidulated (lemon juice) water after peeling to prevent discolouration. You can serve it raw shredded and briefly blanched in boiling water then thoroughy dried and served with thick mayo, highly seasoned with salt, mustard and balsamic vinegar.
You can mash it together with potato, which gives the mash lovely flavour. Alternative, potato cakes.
Most recipes seem to advocate parboiling it. You can mix it with other veg, eg onions, carrots, beans, peas and fry them in extra virgin olive oil then finish in stock and seasoning (dill was recommended).
Hope this gives you some ideas. Another has come to mind is the combination of chopped fried bacon and onions with the cooked celeriac. Fried bacon. onions and peas (not fried) work well together too.
Kate