You are going away, to some place isolated… in space, of course. You will only be around one other person. You can take an allotment if 1GB of personal media with you (text, video, music, games, pics, etc.) that you will be able to access in your free time indefinitely at will.
The other person will also take 1GB with them, but you won’t be able to talk to them until you’re on the journey.
You will have access to any knowledge resources to perform your function and keep you alive. You will never return to a point where you can get new external media. Any additional media you ever access would have to be created by you and or your travel partner with what you have access to.
You will also not know the sex of your partner, but they have willingly taken the same risks to embark on the journey as yourself, and will have a similar mission.
Text of an average book is 100,000 letters; with a very smart and optimized compression/prediction algorithm (which hopefully is far smaller than 1GB), it is reasonable to expect a single char to be less than half a byte in size, so 50kB per book (saving without covers of course), this would mean around 20,000 books in a GB (not really, the compression algorithm probably also takes quite some MBs)— which should be enough for quite some time.
Even 7zip can compress a large text file to less than 25% of it’s original size. The installer is less than 2MB. There are even better compression algorithms for text than 7zip though.
I’m not sure where you’re getting that value. The low end of word count for a novel is 50,000. If we say the average word is only 5 characters, we’re looking at a quarter million letters and another 50,000 spaces for a short novel (200-250 pages). Throw in some more for punctuation and formatting, of course. If you’re a fan of big epic fantasy/sci-fi you’re probably closer to a million words.