The complete Slough House/Jackson Lamb book list in order of publication along with reviews –

Slough House 0.5 – Reconstruction

Slough House 1 – Slow Horses

Slough House 2 – Dead Lions

Slough House 2.5 – The List

Slough House 2.75 – Nobody Walks

Slough House 3 – Real Tigers

Slough House 4 – Spook Street

Slough House 5 – London Rules

Slough House 5.5 – The Drop (US title: The Marylebone Drop)

Slough House 6 – Joe Country

Slough House 6.25 – The Last Dead Letter

Slough House 6.5 – The Catch

Slough House 7 – Slough House – February 2021