The Nikon EM is a good camera in a compact, easy to use design. It uses an automatic aperture priority auto exposure system. To take a photo with the Nikon EM... you just set the aperture on the lens. You then focus and shoot. The EM will automatically set the shutter speed for you. If your aperture forces the shutter speed outside of it's safe range between 1/30 to 1/1000 of a second, you will hear a beep which tells you to change the aperture.

It was introduced in 1979 and that's the problem. These cameras are getting old and many require routine service. The problem is, it's difficult to find camera shops that will service them. I have checked with 4 online camera repair facilities and only 1 would service the EM I had and they said it would cost $125 just to look at it. Extra for parts... IF they had them. If you look on eBay you will see that you can usually buy them for less than that. And my own personal camera guy that I've used for several years will work on just about any 35mm SLR film camera except the Nikon EM. I don't understand all the technicalities but apparently this camera really was not made with future service in mind.
I have purchased 5 Nikon EMs on eBay and 2 of them were dead on arrival. Those were donated to the parts bin as nobody seemed to want to work on them. The three that worked worked great and took great photos.

Make sure it works

Bottom line... if the camera works... it's great... but if it breaks it will be cheaper and easier to just buy a new camera. For this reason I would avoid purchasing this camera unless you know it's working and in good shape. For that reason it is not one of the best cameras to be looking at on eBay. With most 35mm SLRs from the 70's & 80's... if the camera doesn't work, you can usually have it repaired for around $100 and you wind up with a great camera. Such is not the case with the Nikon EM.