Technically the book is correct. All of the digits. But in common speech we speak of having ten fingers.

in daily conversation people would say 10 fingers, but anatomically thumb is different, thus sometimes if is not referred to as finger.

My wife and I (native U.S. speakers) agree. We have "ten fingers." This seems completely natural. To say "eight fingers" just sounds weird, unnatural, and wrong. This isn't a case of just being precise. The word "finger" is ambiguous. Depending on context, it can include the thumb or not. There are many examples of words like this. For example, 99% of the time the word "dog" includes both male and female dogs, but in some contexts, the word "dog" can mean specifically a male (the female being called a "bitch." But don't try to use that word unless you are a dog fancier talking to other dog fanciers!)