I am slowly finishing the translation of the next book in the series but I couldn't stop myself from getting excited about the author's newest book. Hopefully its wonderful and becomes a series.
It's called "異人館画廊 盗まれた絵と謎を読む少女" (translated Foreigner's home art gallery: The stolen painting and the girl who reads mysteries). Apparently its a mystery novel. Here is a website advertising it: http://cobalt.shueisha.co.jp/news/mystery/ (Japanese). And the illustrator is Tsuguko Shijima.
(Icons are pieces of art or paintings that contain complex iconography by hiding unique meanings in its backgrounds or objects. Chikage, a girl who studied iconography in England, learns that her grandfather passed away and returns to her homeland Japan. At the gallery currently run by her grandmother, she is asked to judge a pair of paintings. Apparently those paintings were stolen pieces and come with a dark history...?!)
Comment from the author:
図像学者の千景は帰国子女。祖母の画廊に集まるのは、画商や女優や占い師？ 奇妙な面々とともに事件の解決に乗り出します。絵画にまつわる謎とともに、 千景の謎や幼なじみ（？）の透磨との関係もお楽しみください。
(Chikage is an iconographer who has returned to Japan. The members who gather at her grandmother's gallery are an art dealer, actress and fortune-teller? She struggles to solve a mystery along with these strange people. Please enjoy the mystery evolving around the paintings and the mystery of Chikage and her relationship with her childhood acquaintance(?) Toma.)
Character Relationship Graph: (In Japanese only)