As each of the later Harry Potter volumes came out, we heard plenty of stories about people who read them straight through in 24 hours or less.
Really it depends on the length of the book. Other factors are the level of writing (how dense or simple), your own reading fluency, and the degree of comprehension you’re trying to sustain. Some practiced readers are very fast, even without learning speed-reading techniques. Others, like me, read fairly slowly. I rush only when I have a deadline. (If a book isn’t worth a slow, thoughtful read of every word, I won’t bother with it.)
Why don’t you give it a try and find out what you can do?