Most senior people suggested me that I'd better read the English editions of the technique books. It is true if you don't allocate special time to study English because it'll make your English language sense better. (Not too much, I think).
But if you already have a fixed amount of time to learn English, you don't need to read English version of the tech books. Or even harsher, it is kind of time waste. Let's make an analysis: how many useful new words you can get from a tech book? How well the sentences are expressed in a pure technical book? Can it be better than the articles of TOEFL or GRE? Far far away~!
Just as one canonical rule for Software Development : "One simple & clear responsibility for one class/method." So, the same, when you wanna improve your English, study TOEFL/GRE; when you wanna improve your technique level, read the book in your native language --- UNLESS: the book is translated quite badly :)