Not his best book (in my opinion), but a great one. It's a remarkable example of the "whole is much better than the parts": the start is a bit boring, the pseudo-dialogs with the fish are a bit silly and the climax is a bit disappointing, but when you close it you get the feeling that you experienced something great.
What is always superb in his work is the language economy, the to-the-point sentences, the lack of useless words and meaningless descriptions. Hemingway invented the modern prose and all of us readers and writers owe him a drink.