Before Slough House Mick Herron wrote the Oxford Series of mysteries. This series has some links to Reconstruction and Slough House but is basically an unconnected standalone series. I will be reviewing them over the coming months –

Oxford Series 1 – Down Cemetery Road

Oxford Series 2 – The Last Voice You Hear

Oxford Series 3 – Why We Die

Oxford Series 4 – Smoke and Whispers

Herron also released a short story collection – All the livelong day and other stories

In between Slough House books Herron released an unconnected standalone – This Is What Happened