First, you should read the books before this one to completely understand and appreciate the importance of the events in this novel. If not, you will be completely confused and get lost easily.
Second, if you, (like me), have enjoyed the other books and fallen in love with the characters of Ethan, Nathan, Brendan, Casper, Sean, Skye, etc. this will be a difficult read for you.
This book is hard to read and you might find it heartbreaking. However, it is a good read. I am a huge fan of Mark's books and I found that, once again, he had not let me down with this novel. I was on the edge of my seat and felt like I was feeling everything the characters were.
This is a great read, but prepare yourself for a story unlike the others.