Peter Robinson, ian Banks, the rest of LeCarre, the whole "Bosche" series, and - of course - the incomparable James Lee Burke.
Oh, and, for the "period" touch, search for this thread :-
"Dr Thorndyke" now complete
for Harry's excellent Thorndyke canon, a bit about them, and downloads, from the MobileRead Library.
They'll make you think all right .... much more rewarding than Holmes, I reckon.