A Riddle

Next to my night stand there is a stack of books about baby names and pregnancy. Tobin and I were talking about names the other night, so I grabbed the top book, which was a baby name book. The bottom 1/3 of the book was wet; not dripping, but noticeably wet. I checked the other books, but none of them were wet. The floor was not wet, and there was nothing on the night stand that could have spilled on this book. I'm stumped! How does the bottom of the top book get wet when nothing else around it is wet? I asked my kids and my husband if they know anything about it. They don't. Strange!