Why We Sleep: The New Science of Sleep and Dreams

melatonin helps regulate the timing of when sleep occurs by systemically signaling darkness throughout the organism. But melatonin has little influence on the generation of sleep itself:

Information on what makes us sleepy, sleep soundly, and feel awake and alert. It covers a broad range of tools for anyone wishing to improve their sleep and wakeful state. The science and logic for each tool are described.