When I’ve said, “x is so good I can’t put it down” I’ve used this simply as a metaphor for really really good. However, at age 53, I haven’t felt this way since I discovered Stephen King, in the 80s. Last night I stayed up for most of the night reading half of book 5. Although this is rooted with a sci-fi setting and plot structure it crosses many genre in a fun and engaging way. So far there are many scenes, throughout, that there are alien races that make Nazis look like a kindergarten tea party I somehow can’t stop going to the next level of the story. I really can’t recommend this series more.