The Girl with the Dragon Tattoo is the first in Stieg Larsson’s Millenium series. It’s £0.99 at Kindle UK today as part of the UK Daily Deal.
Buy at Kindle UK
And the first in the continuation of the series by David Lagercrantz, The Girl in the Spider’s Web, is also £0.99 right now.
Buy at Kindle UK
An omnibus of the first three titles in this series, the ones written by Larsson himself, is £0.99 at Kindle UK today: https://www.amazon.co.uk/dp/B01CUJA454
The titles include: The Girl with the Dragon Tattoo, The Girl Who Played with Fire, and The Girl Who Kicked the Hornets’ Nest
This omnibus (with the first three titles in the series) is £0.99 again at Kindle UK. The link in the comment just above is still good.