Novel by Samuel R. Delany that was the joint winner of the 1966 Nebula Award with Flowers for Algernon.
Rydra Wong is enlisted by her government to crack the Babel-17 code which their enemy is using. Rydra realizes that it is not a code at all but a language that completely lacks the pronoun, and the very concept, of I. As she learns the language, she slowly begins working against her government without realizing it.
This blatant interpretation of the Sapir-Whorf Hypothesis dates the book to some degree, but it's still a cracking good read. Rydra is a huge departure from Delany's other heroes, but goes along with many practice women in his other books. As of 2001, it's been published with the short story Empire Star, which has some loose connections with the novel.