I haven't read as far as Arsenic Labyrinth, but thought Coffin Trail and Cipher Garden were fantastic, the characters and the cold case review angle seemed really fresh.
I'd also really recommend checking out Rupert Holmes' Where the Truth Lies http://www.bookrabbit.com/catalogue/detail/bookid/1512388/Where-the-Truth-Lies - he captures the period (flicking between 1950s and 1970s Hollywood) so well and it's such a page-turner.