OK, I'm also a committed non-Christian but this book is great. The 'faith' aspects do not detract from what was clearly an epic adventure and in no way spoiled it for me. If anything, I knew about these before starting the book and was releived the author had not over-egged this aspect.
You'll have to look very hard indeed to find someone - believer or non-believer - this adventurous who can also write about it in such an engaging way and on that basis alone, it is an absolutely fantastic book. Buy it, i couldn;t put it down.