The make up of the Marshall ED-1 Compressor is really simple and easy to follow as it has a series of four knobs that each will control a different aspect of your sound. From right to left it has knobs for compression, attack, volume, and emphasis, the latter of which is kind of like a tone knob. This is pretty much all there is to it and anyone with any sort of experience with guitar pedals or compressors won't have too much trouble with it. I don't have the manual for this pedal but it is easy enough to use that you don't really need it.
The sound of the Marshall ED-1 Compressor is a bit above average and will definitely do what it advertises to do, which is compress your guitar signal in any way you see fit. I usually use this pedal with a Fender Strat and a 1976 Fender Twin Reverb and I'm always pretty happy with the results I am able to get. There is a good amount of control over your tone available, which adds to the overall number of sounds that are possible with this pedal. While I've used some better compression pedals before, the Marshall ED-1 Compressor is a nice pedal in its own right.
I first used Marshall ED-1 Compressor guitar pedal about two or three years ago and since then it has always done well for me. I like the overall tone it has and the ease of use makes it a good option for players on all experience levels. The price is very reasonable if not downright cheap and certainly gives you some bang for your buck. While I prefer the Boss CS-3 compression pedal to this one, the ED-1 is a good pedal and will last a while if you treat it properly. If you are in the market for a compression guitar pedal I would encourage you to check out this pedal as well a few other pedals out there like the CS-3 or the MXR Dynacomp to see what will work best for you and your situation.