Legal/financial advice: This is a scam right?

So recently I decided to try and sell some of my books I don’t need any more last quarter, and I thought hey, I can use facebook and people on campus will see it and buy it and I won’t have to ship them. Well some guy in England shoots me an email and tells me he wants to buy them and instantly starts giving me orders, telling me he’s going to send me a check for more than the amount of the book ($50) and that I should pay DHL with his money and wire the remaining back to him via Western Union wire transfer. I got suspicious and wondered why I had to pay the shipper and why I couldn’t put the remaining money with the book. Also, he could barely speak english and it took me forever to figure out his emails. So I tell him I failed the class and I still need the book, and he says but your selling another book, I’ll take that one. At this point, I just no, I don’t want to send you anything, sorry. He says he already sent me money, so I then I said I’d destroy the check as soon as I got it. Here’s the kicker… I check my mail a few days later and I have a cashiers check for $1600. wtf mate? This puts me in an odd position. Is he money laundering? Can I even consider cashing it safely? I will never sell things on facebook again.