@johanp: This is the list of preinstalled dictionaries:
De-En
En-Cs
En-Da
En-De
En-El
En-Es
En-Fr
En-It
En-Lt
En-Lv
En-Nl
En-No
En-Pl
En-Sk
En-Sl
En-Sv
En-Tr
Es-En
Fr-En
It-En
There are other places than the Obreey store where you can find cheap/free dictionaries, including En-En ones. Google is your friend
And also search for the information about PB dictionaries here on MobileRead. Especially, if you can manage the language, the German PocketBook forum here has a lot of relevant information.