The common inkcap (Coprinopsis atramentaria) is, as the name might suggest, very common but because they 'liquidise' very readily they are often hard to identify and, in any event, are only around for a couple of days! They are also inclined to be quite variable in appearance.
This is very much a species of woodland and, in particular, tree stumps, twigs and general wooded debris that have a soil covering but you can also find them on grassland where there is buried timber below the surface. Generally solitary or in small groups they are visible from spring right through to the autumn.
They are considered edible but I think you would have to find them pretty fresh and cook them quickly to get them at their best. You should also avoid having a glass of wine with them as they can have nasty effects when eaten with alcohol! Indeed, it has apparently been used as a drug to help cure alcoholism. The black liquid has also been used as a drawing ink.Coprinopsis atramentaria: the common inkcap