Things get interesting right away with this one, as the short prologue offers just enough to intriguingly set the stage, and the structure of the main part of the book is immediately attention grabbing. From there a lot of interesting little details and mysteries accumulate, and the examination of the non-linear aspects of the story are particularly well done. There are numerous carefully built, excellent twists and a slowly escalating tense atmosphere.
Character development is necessarily a bit different and more subtle than in traditional stories, but is there if the reader pays close attention and I thought quite good. I can see some readers losing patience though. Also, some of the end resolution was a little lacking to me and I’m not entirely convinced about the direction of the series going forward.
Derailments of Thought 
Overall though I found The Empty Box and Zeroth Maria a thoroughly engaging and satisfying read, and highly recommend it for any light novel fans who can handle its mystery/thriller aspects and don’t mind applying some patience and effort to their reading.