I just thought this little invention was quite clever.
“Lampmark is a LED powered lamp for night reading. It automatically shuts off when covered with a book while at the same time it serves as a very intuitive bookmark.” - Damjan Stankovic
Though this is merely a concept design. more information can be found on the products detail page. Damjan is a designer from Serbia, you can see more of his great and innovative (re)inventions over at his website, Relogik