V. Aspect particle le了 and modal particle le了 used together without a quantified object or duration between them indicates that the action has been completed. Such a usage is the same in meaning and function as one that takes only the modal particle le了 at the end of the sentence.
Wǒ kàn-le shū le = Wǒ kàn shū le (Kàn is stressed.) 我看了书了。 = 我看书了。 I've read the book.