Reading a book you've already read is definitely a good idea. Seeing the grammatical forms you might have heard, and even tried to use, written out (and well-edited!) was for me immensely helpful.
It also helps that you already know what happened: if you don't understand a passage, no big deal. Just skip over it. It beats checking the dictionary many times per page. There's some truth to the notion that you can figure out what words mean from context, but it's often not possible. However, if a word is used over and over, as many important to the text you're reading are, you might get enough context to work out what they mean. If you can't, then reach for a dictionary.
I tried something similar recently. I am learning Japanese and so I dumped audio track from anime to my mp3 player. It seems to help with understanding the language. And it was fun to guess what is going if I haven't seen the series for long time.
This also works if you pickup a series halfway through, having read the first half in your native language, and then finishing it in the new language. I've done this with Harry Potter. Before moving to Canada at 14, I read the first 4 in Romanian and the 5th and/or 6th in English. Since many of the terms were found in previous books, or since i knew them from the movies (example quidditch which the translators decided to translate. Still not sure how they got with the Romanian term from quidditch)
It also helps that you already know what happened: if you don't understand a passage, no big deal. Just skip over it. It beats checking the dictionary many times per page. There's some truth to the notion that you can figure out what words mean from context, but it's often not possible. However, if a word is used over and over, as many important to the text you're reading are, you might get enough context to work out what they mean. If you can't, then reach for a dictionary.