tl;dr: Backlash delivers on the set-up at the end of Spymaster.
Backlash has a straightforward story whose beats should be evident within the first few pages of starting the story. Scot Harvath has been captured by the Russians and has to fight his way out in an inhospitable terrain.
What I liked
Backlash manages to break the cycle of ennui that was creeping into the series with a different kind of story, albeit one we have seen before in other series. This kind of escape story, though predictable, is still exciting and is fun to read in the Scot Harvath context.
What Could Be Better
Beyond the usual pro-US/anti-Russian rhetoric that is a staple of Western Action-Thrillers, there are a couple of things that Brad Thor could have done. The first one is to make the escape story itself a bit more unpredictable. The second is to make the last few chapters into a book of their own. Daniel Silva tackles a similar topic much better in his series by spinning off important story arcs into their own book.
Backlash is a fun read. Scot Harvath fans will love it but it palls when compared to other books in the same series.