I've read all of the Tier One thrillers and am anxiously awaiting #6. The Ember Team continue to deal with many real world problems and issues confronting us today. SPOILER BELOW SO BE AWARE!!!
I quickly picked up #5 the day after completing #4 of the series. It was great to continue to deal with many of the same characters, but at the same time I was wanting a bit of closure. Specifically, I wanted to know if the two main Russian characters would be taken out and whether the mole in the DNI office would be identified. Fortunately, the mole is identified and really taken care of, and one of the main Russian characters is also eliminated. I was not expecting the loss of Ember as a physical facility nor of some of the Ember team. I guess #6 may deal with the other main Russian adversary as well as the Russian president/premier.