"Based on the book by Roberto Saviano". Not really...Inspired maybe

So back when watching S1 i decided to pick up the book by Roberto Saviano since the series is supposedly based off the book. Eeeeh...no. Now this is not a rant since both book and series is great, i just wondered why they say its based off the book. Sure he might have read it and got inspired since the book is also set in Naples and chronicles the criminal families etc and talks about how Naples is europes drug hub etc due to its port. But regarding events...none of them are found in the book. Literally none. I THINK both the book and series has something about an innoncent girl being killed and torched in a car cause she saw some stuff she shouldnt have. But that is really about it. Am i completely wrong here? Do enlighten me if you can draw some parralels that im missing(Except the setting)