I have
this case as well as a black case that IxiaAurea linked above. Yes, they're both sleep cases, which are so convenient once you use them, I doubt you'll go back. The magnet is strong enough in one of mine to shut off the reader when I flip the cover back to read, but just place some aluminum foil folded up as much as you need over the magnet area before you snap in the reader and problem solved. It might still trigger if I'm reading while eating outdoors at places with metal tables though

... but that's rare and since it's laying flat on the table anyway, I can leave the flap open when it happens.
I have several other covers, including a Gecko slimfit, which all work, but this one is my favorite for small size and no flaps to get in the way, the magnet on the cover keeps it closed without having an extra flap to deal with while reading.