Kale is an intimidating vegetable -- the black diamond ski run of the produce world.
Its' leaves are thick, it tastes dreadful raw and it can be bitter.
But if you can get over all that, it's a nutritional thrill.
(In truth, it was not until I learned how beneficial it was, that I came to love it.
) First its credentials If you're looking for an overall kale "score" - the SAT equivalent - the ANDI Score indexes all food on nutritional density relative to calories.
Kale scores a perfect 1000.
(Walnuts, for example, are highly nutritious, but highly caloric and hence score 34).
How did kale achieve this...

• High levels of antioxidants (beta carotene, vitamin c and lutein).
  
• High levels of anti-inflammatory nutrients (vitamin k and some omega 3*).
  

Oxidation (which is happening all the time in our bodies) is critical for life but it also damages cells.
A state of high oxidation as well as high levels of inflammation puts our cells at a greater risk for cancer hence the benefit of the antioxidants.
There is some evidence that antioxidants not only stop the destruction of oxidation, but actually kill existing cancer cells.

• Strong on the calcium and iron front - all greens score high on calcium but kale has much higher "bioavailability" meaning you absorb more of it (it takes 5x as much spinach to get the same amount of calcium.
  )

What kind to buy There are three common types: Curly, Dinosaur and Red Russian - story book sounding characters who were given names to match their looks.
Red Russian has red veins, Dinosaur has nubly pre-historic bumps and Curly is curly.
The flavor and texture can vary enormously but in general I would say Red Russian is the entry point as it's often milder.
How to make kale taste good

• Remove the entire spine and stem which can be fibrous
• "Flash" steam or sautee (2 mins), until it goes a deep green shade and then stop! You're just past "raw", but only just.
  If you keep going it will turn a muddy green/brown and lose its flavor and cancer fighting properties.
  
• Sweeten if needed.
  (Some kale can be a bit bitter but this is not a good enough reason to not eat it! If you need to, drop in a touch of honey or agave or a few dried cranberries.
  )
• Add other things to tame its greeness.
  (Sauteed onion or sauteed fennel get very sweet when cooked hence a perfect partner); nuts (pine, sunflower seeds or sliced almonds); dried fruit (cranberry, apricots, or small bits of fresh plum or fig)

Recipe Sauteed Kale with Sweet Bits (I use a variation of this simple recipe 80% of the time I cook kale.
It's a perfect side with meat or fish or dished over rice or quinoa.
) 1 T olive oil 1 onion sliced (or 1 head of fennel sliced or both) 1 bunch of kale (cut into edible sized strips) 1 T dried cranberries 1 T sunflower seeds (can use roasted pine nuts, or slivered almonds) Salt & pepper (don't skimp on the salt) Heat oil in pan until very hot! Add onion/fennel and cook until nicely browned and soft.
Add kale and sautee for about 2 mins or until kale is bright green and slightly tender.
Add nuts and fruit and s&p.
Remove from burner and let sit for 2 minutes to allow the ingredients to infuse their flavors into the kale.
*See this primer on omegas.