Dictionaries are difficult to use because they give generic definitions of words rather than the specific meanings & senses of words that are expressed in the texts that you're reading. Also, I think that automated translation services, e.g. Google Translate, & web interfaces that use such services to show definitions or translations when you roll the mouse over, typically do a poor job of translating/conveying the authors' intended meanings.
With that in mind, I recommend buying 2 copies of each book, one in your first language & the second in the target language. This way, you'll have expert translations of the most appropriate choices of words, phrasing, & expressions that best match what the author is conveying. It may be more difficult to switch between them than an automated translator or dictionary but I think the quality of the language learning you'll get out of it will be worth it. I also recommend reading texts more than once; first slowly & checking with the first language translation, then again hopefully checking with the translation less or not at all. Follow up with reading the text again the following day, & the following week (AKA "spaced repetition"). Multiple encounters with new words, phrases, & patterns ensures that you're more likely to remember & understand them when you encounter them in the future.
You can similarly switch between translations with video quite easily, since many DVDs, BluRays, & streaming video services offer translations in multiple languages.
I hope this helps! :)