If I liked the Alex Delaware novels by Jonathan Kellerman

[AliceAir]

Which I did - are there any similar series I might also like?

You could try Michael Connolly's 'Harry Bosch' series, Sara Paretsky's 'V.I. Warshawski, Maj Sjowall and Per Wahloo's 'Martin Beck' series, Abir Mukherjee's recent crime novels, Robert Crais's crime fiction, there's a great series by George P. Pelecanos, anything by Elmore Leonard or Carl Hiassen, Lawrence Block's 'Matt Scudder' series.

Oops also Laura Lippman.

Oh Dottie - thank you. Lots to investigate there. I’ve read some of the Harry Bosch ones and I did like them.

dottie just wanted to thank you again. Also, I checked out the Abir Mukherjee series and saw that one of the main characters in called Bannerjee. My late df’s best friend was called Bannerjee and, seeing the name like that, I got all unexpectedly emotional. I will definitely read them but perhaps not quite yet!

I’d recommend:

Will Trent series by Karin Slaughter
Charlie Parker series by John Connolly. They’re a bit ‘supernatural’ and very dark, but very well-written stories.
Harry Bosch series is good - I’ve enjoyed the adaptation on Amazon Prime