Dear Majorix,
My native language is Brazilian portuguese. Since I've come to know Kindle, I started to read in English because there are almost no ebooks in portuguese.
What I've found to work most to learn English is
1) to use
not an EN-EN dictionary in your e-reader, but a translation dictionary.
2) Each time I see a definition, I look to the horizon and, mentally, put the word in funny or deep phrases, imagining a picture to record what that word means. I record it more easily for later passages.
3 If you have to look the dictionary too many times in a book, you're reading the wrong book. Normal people (me included in this case) cannot retain so many new foreign words in a row. With step number 2, the word learned keeps fixing in your mind while you continue to read. If you continue to get meanings, you get lost on the book
and on the word you've searched before.
Hope these 3 steps help.
By the way, get a (legally) free English to Turkish Kindle dictionary here:
http://eb.lv/dict/.