Not really my kind of book - I don't like the letter / diary format either here or when it's been used elsewhere. I also struggled to emphasise with the main character, and there seemed to be very little in the way of checks and balances on the crew of both vessels (surely there should be at least 2-3 people awake at any one time - what happens if one of them falls ill?). The twist at the end was okay but overly rushed. The only upside is that it was quick and easy to read.