This is a tough question because one person's gripping read is another person's dull ramble through irrelevant tangents.
Personally, I get sucked in most by Lois McMaster Bujold books. I'm constantly picking up a well-read favorite to see how she handled Character Conflict X or Plot Development Y and... five hours later, there I am, skipping dinner to read one more chapter of a book I already know the ending to.
Paladin of Souls is a particularly notorious culprit.
Other books that simply will not let me go include Robin McKinley's
The Blue Sword, Brandon Sanderson's
Mistborn, and Jane Yolen's
Dragon's Blood.