The Private Eye Novel: Ross Macdonald and Loren D. Estleman

You are a very pertinacious young man and you are making a nuisance of yourself.
--spoken to Lew Archer in Ross Macdonald's The Barbarous Coast, 1956 (Library of America).

I hadn't worked in a month.  The Internet had swooped in and snatched up all the jobs I used to do, free of charge.  You could track down an old high school sweetheart, a deadbeat dad, your great-great-great-grandfather's crib in the Old Country, complete with a virtual walking tour of his thatched hut.  No phone time, no embarrassing conversation with a stranger, and best of all no bill.
---  Amos Walker in Loren D. Estleman's The Lioness is the Hunter (Tom Doherty Associates, 2017).

Things have changed since the fifties, but  Estleman's Amos Walker and Macdonald's Lew Archer both do most of their work on the phone and in person, putting themselves in dangerous situations.  I prefer detective novels written in the first person (so that we are not aware of anything the narrator is unaware of) and that use very specific locales: Archer working in a burgeoning Los Angeles in the fifties and Walker in the decrepit Detroit of today.  Both detectives are cynical former cops, always hoping to get the best from people and usually getting the worst; both are long-divorced loners who try to cover up their insecurity with snappy banter.

We know more about Walker as a person than we do Archer; Macdonald is more interested how and why people commit crimes and Estleman cares more about survival in a hostile environment; in these two books they are working at the top of their form.  Macdonald is directly descended from Hammett and Chandler, i.e., his plots are often confusing and difficult to follow, though it usually comes around full circle to the place and people with whom he started, while Walker usually follows a fairly direct path from his dusty office to a violent confrontation.  Archer's cases often originate deep in past behavior while Walker's are more immediately dangerous. Walker and Archer are both are on the side of the exploited as they search for the exploiters and bring them to justice, of one kind or another.