Later I read more about them in Alicia Silverstone's book A Kind Life, and she also writes about them here
(the photo above is also from her website).So I was determined to try them... thwarted only by the fact that they are really expensive...so I kind of forgot about them for a while.
but you know how i've got this great husband who buys me treats? he got me some umeboshi plums. they are amazing in a strange way. they are really sour and salty and pickled. they are meant to be good for your digestion or if you have a hangover or if you've indulged in too much sugar. They taste really strong so if you cook with them you may only need to use half a plum... and you can just mix them with rice, or eat with a cup of green tea (i have done a lot of research about this by asking a japanese friend on facebook), so far i've just had them on their own and they are strange and sort of wonderful.