Your "waste a day a not even know it" description stuck with me. Here are some offerings that can be read in about one or two sittings. At least for me they were the kind of books that you wanted to read in a day:

Classic (or semi-classic):

Of Mice and Men, John Steinbeck: good story about drifters looking for work in the fields of California

Johnny Got His Gun, Dalton Trumbo: IMO the greatest anti-war novel ever written

The Crying of Lot 49, Thomas Pynchon: quirky story from a genius writer

Trout Fishing in America, Richard Brautigan: whimsical, not about trout fishing at all (well, sort of...trout fishing is mentioned a few times). Brautigan had a great imagination and there is an endearing innocence to his writing. Anything by Brautigan is a great way to "waste a day" ...most of his stuff can be read in one sitting

Modern Tales of Drama for the Young At Heart:

Bright Lights, Big City by Jay McInerney: girl leaves boy. Boy turns to cocaine and partying in NYC with his buddy, desperately seeking ways to get girl back. Boy has a few laughs along the way. Written in the second person and ends on an upbeat

Less Than Zero by Bret Easton Ellis: rich college preppies in Los Angeles looking for bigger kicks find meaningless instead. Kinda depressing, but a good story