Recently I have read the rest of Peak up to Moleskin #2. So now that I'm in about the middle of the story, this is where it has gotten really interesting. Peak has been climbing up the mountain trying to reach ABC (Advanced Base Camp). Holly was up the mountain with Zopa usually earlier than Peak because it was hard for her to climb. Peak had a sore throat and it was extremely hard to talk for him. Sun-Jo got so sick he puked many times during the night.
I don't see how Peak was able to survive the climb. If I was climbing Everest I would've already given up. Here's a quote: "You don't look to well." he said "I don't feel to well." I croaked back. I think this quote shows that Peak knew he was sick and other people can tell by looks. I suggest you read Izzy's blog because I think she gave a great explanation of Zopa and Sun-Jo, some of the most important characters in this book.