Msnbc.com has an interesting article explaining why people get lost in good books. You can read the full article here.
"Part of the reason we get lost in these imaginary worlds might be because our brains effectively simulate the events of the book in the same way they process events in the real world..."
Apparently, people were hooked on to a brain scan and were told to read a short (1500 word) story. Later the researchers looked to see if changes in the story caused brain activity to change. It did.
The article ends with a little blurb about differences in readers - some people see pictures when they read while others don't - and how those differences may make people more or less of a reader.
Do you see pictures when you read? Reading has always been like watching a movie for me - pictures, voices, the works. For a long time it was hard for me to listen to audio books of books I had previously read because the voices so rarely matched what I thought they should sound like. On the other hand, my husband (who does enjoy reading, though not to the extent I do) doesn't see or hear anything. Reading is simply interesting words on paper to him. The characters are "real" but there are no pictures, etc to go along with them.