Memorization techniques?

I have a 25 page rhyming poem that I need to memorize by the end of next month. I've found that after I memorize the first five pages and go on to the next five, I often forget the first five and I have to go back and repeat the memorization, which takes an incredible amount of time. Does anyone have a special memorization technique (other than rote repetition) to help me memorize this poem?