That sounds like an extremely interesting book.
It actually is. I actually got a chance to talk to the author and he had changed his opinion since the book was written about which planet it was. Oh, and the ice (and 40 days of rain) came from an “ice moon” that accompanied this rogue planet and basically got close enough to the earth to reach its “rouche limit”. https://en.wikipedia.org/wiki/Roche_limit
His argument is that much of it fell to earth on our poles, instantly creating catastrophic tides and giving us the sea level we now enjoy. He gets into the history of the wooly mammoth and the condition in which we find them today - and how they probably died.