As you start falling asleep, your book falls on your face. (Beware of hardcovers and massive paperbacks)
You fall asleep mid-sentence.
You don't sleep until late, or at all.
You ignore the fact that you have school/work in the morning.
The neighbors may think you're a vampire, since your light is on throughout the night.
You tell yourself, one more page, one more chapter, but then feel oddly sad when you come to the end.
Likewise, you might feel like you finally found meaning in your life again after finally finishing that book.
Text messages/phone calls from friends go unnoticed until morning.
If you share a bed with someone...well, maybe you should avoid doing those weird voices you do while reading, and maybe the outbursts of emotions, too.
Your parents might walk into your bedroom to ask you, "What the hell that racket is."
Decide that sleep does not exist when you have no school/work the next day. Hey, it's summer, enjoy it!