Reading and translating is a great way to learn new vocabulary because you read a book and translate the words you don’t understand. Now, there are two dilemmas: what books should I read and what words should I translate.
You can read whatever you want as long as the topic interests you. Some people will say that if the material is too advance for your level then you won’t understand and you will soon get bored reading it. I totally disagree. If your hobby is photography and you read an excellent article written by your favorite photographer then I am pretty sure you won’t get bored translating the words you don’t know, even if there are a lot of unknown words.
Graded readers are books graded on levels of difficulty and they are specially created for learners of English. Graded readers use simplified language but that does not mean they do not use proper language. Each level uses a particularly number of words such as: level 1 is restricted to 500 words, level 2 to 600 words etc. In other words, you can read and understand an entire book if you know 500 words. Graded books make a good reading but I don’t think they are very useful for you if your purpose is to learn new words and improve your English.
Some people say that children books use simplified vocabulary. I totally disagree! Some of them might use simple words but many of them use not very common vocabulary. For instance, the story of Thinker Bell, one of the stories that I read for my daughter, uses words that I personally never used. I understand the words from the context but they are not familiar words for me (example words: tangle, darted, gust, meadow, budge, tamed, sip). That’s not to say it is a bad thing, you can translate them, see how they are used in the context, and learn them.
Newspapers are difficult to read because they use a lot of passive constructs. Although I believe that the passive voice is not so difficult to learn, many learners of English find it impossible to comprehend and use properly. So, newspaper might be difficult to read at the beginning, but it is definitely helpful when it comes to passive voice. Of course, there is a lot of vocabulary that can be learned through newspapers.
Read and translate as much as possible. At the end you remember many words and grammatical structures, and definitely your English will be greatly improved.