As I actually expected , Cook knew he'd had enough and has stepped down at the logical time. Think management would have preferred him to stay on for another year but he clearly no longer had the spirit for it ....hopefully Root (presumably) will be as ready for the task as Cook himself suggested he was...
Equally unexpectedly some fairly ungenerous assessments of his tenure on here but I'm not going to argue about that - everyone is entitled to their own prejudices
For my part I think he did a mostly good job : although not a natural leader he got the best out of quite a mixed bunch of characters to win important series in India and SA , as well as winning two Ashes series ; and if he failed at the low point - the disastrous Australian tour of 2013/14 he had the gumption to stick around and preside over the (still incomplete) recasting of the team. His critics (on here and elsewhere) will never agree but I think he'll probably be seen more kindly in hindsight than he sometimes was at the time.
Maybe not by KP