"Suetsumuhana", volume 5 in the Hikaru series. The readers got to observe the positive relationships between Koremitsu and all previous heroines, in a small cafe space and from the vintage point of a new heroine. This volume is currently my favorite in this series: if this was a more conventional mystery novel, the readers basically got the unknown killer's perspective, a very interesting angle to see all actions unfold. That, and I enjoy seeing Koremitsu benefiting from all his previous efforts.
The extra goods that came with the special edition was also great -- I can now attach voices to the dialogues I have been reading, thanks to the drama CD. I hope this series gets animated.
Previous (2012-10-17): "The Call of Cthulhu and other Weird Stories" by H.P. Lovecraft
Next (2012-11-08): "And Then There Were None" by Agatha Christie