I am a Sci Fi and Fantasy fan, and I have seen Simon Green on the shelves over the years but never bought one of his book. Jim Butcher is currently my favorite writer, I also love Scott Lynch, other writers I like include Michael Sullivan, Larry Correia, William Dietz, David Webber, Patricia Briggs, John Ringo, Laurell K Hamilton (the early works), plus a bunch others.

So I want to start reading Simon Green, which books do you recommend I start with?

Also, I saw a book on Scribd, Casino Infernale, but I don't see it in the Books section, so which series does it belong to?

Best,
AJ

"Casino Infernale" is part of the Secret Histories series. Where you should start depends on your personal taste.
If you prefer swords & sorcery tales, check "Blue Moon Rising", the beginning of the Forest Kingdom series and the spin-off "Hawk & Fisher" series.
If you prefer space opera in the vein of "Star Wars" and "Warhammer 40,000" I'd say that "Deathstalker" is the right book for you. In my opinion "Deathstalker" is the best work of the author.
If you prefer urban fantasy, give "Something from the Nightside" a chance - a very entertaining and creepy novel!
Or, of course, you can just start with the latest series - "The Dark Side of the Road" is a great supernatural crime mystery.
I hope that I was able to help!