I highly recommend kohlrabi root, which tastes like broccoli stem, but I don't have much to say for the greens, which have an off, sea-weed taste (or maybe the ones I'm eating had gone bad).
For dinner tonight, I washed a bunch of pink turnips and a bunch of kohlrabi. After removing the greens, I peeled the roots, keeping the peels for my soup stock, and I sliced the roots. When you peel pink turnips (which have fantastic greens), try to take off as little as possible: turnip skins are thin, and much of the color is near the surface. Kohlrabi, on the other hand, must be peeled with a paring knife; the outermost layer is rather tough and woody. I sautéed the sliced roots in olive oil, with a little salt, and then added the chopped greens, covered, and steamed.
Meanwhile I cooked a small pot of quinoa — one-to-one water to grain by volume, with a little salt, brought to boil, and simmer covered for ten minutes (or longer with more water). We have delicious dried sweet red peppers and dried tomatoes right now; I diced a few of each and included them. This, it turns out, was a mistake. I like quinoa, but the tomato-and-pepper taste is slightly off.
Overall, an ok but mildly dissatisfying meal.
Turnip, kohlrabi, and broccoli are all members of the Mustard family.