I want to buy a statistic book to study during my holidays, but I don't know how to choose.
Can you give me some suggestions?
It depends on what you want to learn and even more so on your background.
If you haven't taken multivariate calculus then you need a basic text.
My advice would be an older edition of wackerly that you can pick up cheaply at half.com
In fact I just used the 7th edition and I have my sixth edition with comments throughout it.
If you were closer I could mail it to you with the solution manual too.