Melatonin is addictive, does work (I tried it), but I wouldn't suggest it. Maybe if levels in the body are actually low, than it can be a good supplement.
Melatonin is produced by the body but the amount we produce reduces slowly as we age ... which is why babies sleep all the time and as we age we have difficulty sleeping for more than a few hours. It's available in supplement form and it works for many. Give it a try. http://www.webmd.com/sleep-disorders/tc/melatonin-overview
Melatonin used to be suggested as a good antidote for jet lag. Used to do a lot of trans-Pacific travel and it worked very well for me. I don't know what "modern" science has to say about it.