One of the best books on writing properly is the classic The Elements of Style by William Strunk Jr and E.B. White. It has everything you need to know in a small size and is perfect to use as a reference when you are uncertain about how to phrase something, wonder what is the right tense for that, and so on. The Elements of Style is straightforward and focuses on only the necessary. Good writing is a lot about “omitting needless words” something The Elements of Style excels in.
If I had one book to recommend about writing it would be The Elements of Style.
You can buy it for a good price here