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.
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.