Books That Flow

What makes a book great for you?

For me, it's the flow of the writing. Each sentence must carry seamlessly into the next, without a sudden halt of forward progress. If I'm reading and I stumble over a sentence, that lessens the effect for me. Usually it's not the use of big or difficult words so much as just an awkward sentence. One that is written poorly will jolt me right out of the story. That is why I enjoy Preston & Childs so much as authors. Their sentences flow without effort.
(And this is something I'm working SO hard on in my own writing!)

What authors do you feel 'flow' with their writing? Have you encountered those with stumbling sentences?