And we readers don't know how the Epstein drive works. Hence my conclusion: not hard scifi. The way the story is structured (each chapter a separate voice; most chapters a cliffhanger, like a tv series) and characters and crew are portrayed: space opera, with opera in the way of soap opera or telenovela (great word).
I was thinking about why these books gripped me, while usually I get tired quickly of space opera. For me, it's in the quality of the execution. Each book and each chapter gives you direct action via a predictable sequence, while the characters get a little more round each iteration.
