Fiend by Alma Katsu

Succession meets The House That Horror Built by Christina Henry in this taut, fast-paced tale of sibling betrayal as the three heirs - the golden boy, the ferocious middle sister, the dilettante youngest child - to a powerful syndicate rush to fill the vacuum after their father falls critically ill, not realising the demonic forces he kept at bay. 

Imagine if the Sackler family had a demon at their beck and call.

The Berisha family runs one of the largest import-export companies in the world, and they’ve always been lucky. Their rivals suffer strokes. Inconvenient buildings catch on fire. Earthquakes swallow up manufacturing plants, destroying harmful evidence. Things always seem to work out for the Berishas. They’re blessed.

At least that is what Zef, the patriarch, has always told his three children. And each of them knows their place in the family―Dardan, as the only male heir, must prepare to take over as keeper of the Berisha secrets, Maris’s most powerful contribution, much to her dismay, will be to marry strategically, and Nora’s job, as the youngest, is to just stay out of the way. But when things stop going as planned, and the family blessing starts looking more like a curse, the Berishas begin to splinter, each hatching their own secret scheme. They didn’t get to be one of the richest families in the world without spilling a little blood, but this time, it might be their own.