I'm more into psychology than clues, so my recommendations reflect that. I thought ASA Harrison's The Silent Wife was brilliant. Such a pity the author died after only one book.
The Alex Morrow series by Denise Mina started great with Still Midnight and if anything it's getting better. Gritty stories set in Scotland about oh-so-believable characters, the 'good guys' sometimes hardly distinguishable from the 'bad guys', both groups with flawed judgment, weaknesses, compassion, good intentions. You do need to appreciate lower-class British society, though -- these are nothing like PD James' Dalgliesh mysteries.
Two of my all time favourite mysteries are standalone books by authors who also write mystery series. Both are set in Berlin during Hitler's rise to power, and capture stunningly what it must have been like to live through those years. Garden of Beasts by Jeffrey Deaver focuses on an American visiting Berlin during the German Olympics, and City of Shadows by Ariana Franklin deals with the White Russians who'd fled to Berlin after the Russian Revolution.
I think everyone I've lent these books to has loved them. (Both are vastly better, in my opinion, than the authors' series.)
