Made into a Movie

Why is it that suddenly every book is being turned into a movie? I just found out that Audrey Niffenegger's The Time Traveler's Wife is being made into a movie. This goes with a list of other books, both read and unread, which are being made into movies.

The Golden Compass: 12/11/07
I Am Legend: 12/2007
Twilight: 12/12/08
The Jane Austen Bookclub
The Other Boleyn Girl: 02/29/08
Inkheart: 2008

Could it be that I just never noticed before, or that it's something people are wanting more now than they were before? I feel like typing in the name of any random book in the IMDb search box and seeing what turns up - I feel almost sure that anything would. The test? The following are not currently being made into movies:

Charles de Lint: The Onion Girl
Gregory Maguire: Wicked
Jasper Fforde: The Eyre Affair

Guess this proves my theory wrong.