I've been getting these in a CSA box recently and thought I couldn't have them, BUT after checking the stats, they are a summer squash, and right in line with yellow crookneck squash and zucchini for carbs. I decided these are on my alt. plan.
I just peeled, cubed and steamed them, and they are awesome! A bit fleshier than other types of summer squash, but very similar.
I haven't seen these in my supermarket, but a farmer's market would be a good bet if anyone wants to look for them.