You don't need a European book, you need Ireland specific as different things grow in different countries depending on where they are ...........
What do I get in Ireland ...........mushrooms and other edible fungi ( but you need to know what to eat and what not to) including truffles which are one of the most expensive foods you can buy ( if you can afford them)
Young dandelion and nettle leaves, wild garlic, water cress, there are lots of different seaweeds, also mussels, crabs,cob nuts, sloes, blackberries, rose hips, crab apples, quince, elderberries and elder flowers, also birch sap ( http://birchsapwine.com/ ) lots of various seeds, like pine nut seeds, sunflower etc which you can toast and eat as snacks
This may be a good place to start
http://forageireland.com/
https://www.facebook.com/pages/Forage-Ireland/126182967447019
http://fergustheforager.co.uk/
http://www.naturali.co.uk/wild-food-foraging.html