They're reputed to be like pears but harder and more bitter. This is what you see when you cut one open - which, incidentally, is hard work, about as much as cutting a butter-nut squash.
Yes, a lot like pears, but not so much "bitter" as "dry", in both sense. No juice, and no sweetness. No real acidity, either.
So I chopped, peeled, cored, and cubed, ending up with 560g after wastage, ready to turn the lot into Quince Jelly - or, being into historical things, and having the Four and Twenty Blackbirds around to advise, 17th century Quince Marmalade.
"Let your quinces be full ripe, boil them till they are quite tender, drain and sift them as usual; reduce the marmalade (on the fire) to a paste-consistence, stirring continually, according to the quantity of quince-marmalade; refine a pound of sugar to three quarters of quinces; mix them together on a very flow fire without boiling, put it into what form you please directly, and dry as usual."
"Sift" means to push it through a sieve. In fact I used a processor, since life is too short.
They turn red when boiled, and take abut an hour or so to go soft
Then I mixed with the same weight of sugar as of quince (about 500g), using jam sugar since we had some. Heated slowly and gently, stirring and letting it "glop" a bit. It had to stand and go cold part-way through (had to go shopping), and the surface at least was setting nicely when we got back. A little more heating and glopping, and the bottom of the saucepan stayed clear for a moment when stirring, so that was about good enough. I foil-lined a baking sheet, and poured it in.
It's setting nicely, and spending the night in the fridge should finish it off. Then I can chop it into squares ready to serve. If I get 50 pieces out of that, they'll be one WW Point each.
Incidentally, should one be tempted to apply fingers to wipe out the last bits from the saucepan, bear in mind that something that's 50% sugar, even if only "glopping" rather than boiling, is quite hot. Well worth the burnt fingers, though.
(What, no tag for fruit: quince???
More surprisingly, no tag for jam/marmalade, either)