He read the book in one sitting.
Meaning: This means that he was so engrossed in the book that he read it all in one go.
Choice of Words: Read means to look at and understand the words in a book, one means a single unit, and sitting means a position in which someone is seated. When you put them together, "read the book in one sitting" means to read the entire book without stopping.
Alternative Expressions
Related Expressions