FWIW, I'm delighted with the book. While I care about all the members of the Donner Party, I've always been partial to the Graves family, and this is the first major book centered on them -- the Reeds and the Donners get most of the press. Dan works in a great deal of interesting information about the Graves family and about starvation, hypothermia, and other scientific aspects of the story. He also revises the Forlorn Hope's itinerary and gives a explanation as to how the snowshoers went astray. (I wish he'd included a map, but can't fault him for not doing so: finding decent cartography is a big problem for trail writers.)
Various reviews of Indifferent Stars have already appeared on the Internet. Some writers don't like the discursions, others do. Donner Party buffs will, I think, welcome the new information, new approach, and new things to think about.