The writing is top-notch, and the zombie survival scenario perfectly suited to the journal-style that the book is written in. The descriptions are wonderful - a breath of fresh air after reading the tech-manual like Survivors. The environment and atmosphere that J.L. Bourne is able to build is really superb and sets this series apart from anything else. The journal style also allows you to really get inside the head of the main character, get his thinking, his fears and his plans. It's great stuff; it really draws you into his experiences and what the guy is going through. The journal entries steer away from some of the interpersonal/relationship/moral dilemma stuff and focus on the events and matters of survival, which is fine by me, but I thought I'd offer a heads up. If you're looking for interpersonal zombie drama, watch The Walking Dead.
Day by Day Armageddon suffered a bit from a lack of plot direction -- the survivors simply moved from one hideout to the next until the book eventually ended. After a somewhat slow start, Beyond Exile overcomes the meandering plot issues of the first book, sticking to the same story for a substantial portion of the book. And it's a pretty good one--the main character, stranded deep in zombie infested territory, has to escape and evade his way back to safety. It is definitely a page turner, especially for anyone who has ever thought through a bug out scenario. This is bugging out with zombies, my friends.
One element of Beyond Exile that I especially enjoy was the mix of military technology woven throughout. Unlike many zombie stories, Beyond Exile does not write off the military or limit the survivor's weapons to shotguns and fire axes. They get Light Armored Vehicles, A-10 Warthogs, UAVs, laser guided bombs, Abrams tanks and cutting edge zombie slaying tech developed by a mysterious group known as Remote 6. This book has a lot of cool military gear--it brought a smile to my face more than once.
Anyways, highly recommend this book. If you haven't read the first, you can pick up a two-book compilation + a short story on Amazon for $12.24. It's a steal of a deal. The reviews on Amazon give it three stars, but that is because people pre-ordered thinking it was a net-new book, not a compilation. Great read.