Solar sails, even mile-wide ones, don't work for interstellar travel. Especially when course corrections are involved.
I'm hoping that the human factors in this book are better thought out. There's still the whole mystery of what exactly happened that made someone kill everyone and sabotage the ship. The crew are all clones of the original crew, and their uploaded minds were damaged so that all recent memories were erased.
Right now nothing really makes sense, but that could be a sign of a devious and complicated resolution to the mystery. Here's hoping...