This is another excellent entry in the series by this author. I enjoy all of his books, because I've always loved survival and people that do cool things like building safe rooms or secret tunnels. These books are chock full of those kinds of things. Simple things like using motion sensing driveway alerts to let you know when people come onto your property or using motion lights installed at set distances to range targets at night.
The best thing about this series is it's realism. It's not an alien invasion or government conspiracy that takes down the nation and causes all the mayhem, it's when entitled Americans who didn't prepare for even the slightest disruption are deprived and get pissed off when someone who did prepare doesn't hand over half their supplies.
These books definitely lean to the prepper way of view, but come on, you're reading survivalist novels, what did you expect. The preppers come out looking good and the ones who aren't realistic look stupid and are often killed because of it. Even people who try to adopt the right mindset still have ingrained reactions that cause trouble for them or others, because they don't realize the ramifications that their minor actions will have. For instance, suppose you share a little of your food with a hungry person. That's compassion, but when they start starving again, they figure that if you have some food, you must have more and in desperation, they could hurt or kill you. Even if you don't have food, they might believe you're lying to keep it all to yourself.
These are really well written, though, and I think they can help improve the mindset of all of us. Even if you're a person who doesn't like the gun aspect, which I personally think is awesome since I'm an enthusiast, you should understand by reading them how much difference a little preparedness can make to your situation. Maybe the country won't be taken down by terrorists, but look at the situations we have already gone through. Hurricane Katrina, Sandy, Harvey, the California wildfires. If you have some supplies you'll be better off to survive till help comes, or you'll have the mindset to leave early, or you'll have bags with essentials packed so you can bugout(aka leave to go to a safer location). Even if reading these only causes you to throw a couple of bottles of water and a blanket in your trunk in the winter, you'll be glad you did and it'll be well worth it.
This particular book expands on the series in a cool way. The 'Borrowed World' books follow two sets of characters for the most part. You have the ones trying to get home and the ones still at home trying to hold things down. With 'Locker Nine' you get a different perspective. Instead of a large male, you get two small females trying to make their way through hostile territory and one of them hasn't ever trained or even thought about how to act in this kind of situation, making her a liability. While I totally agree that females can be as bad ass as males, this throws an entirely different perspective on it, because people she'd run into probably saw a small girl and thought she was a softer target than a male.
This book gives you several different perspectives to look at things from. You don't have many non-preppers, but you have regular preppers, ones who've got compounds (as introduced in 'Locker Nine'), you've also got special govt operators. It's a cool book and I was so engaged that I read it all in one day, like I've done with all the others. I really suggest people read this entire series, because like I said, even if it causes you to prepare a little you'll be better off. Something as simple as a thermal blanket in the winter and a little water could help prevent your death from cold or loss of a limb from frost bite. If nothing else, it'll make you more comfortable till help arrives.