I read thousands of books, but never learned to write eloquently until I was 18 and was taught to write by someone very experienced at teaching writing. He went through dozens of essays with a red pen, tightening constructions and arguments. I'm convinced that doing is the only way to learn writing, and if you can get 1-on-1 guidance and detailed feedback, it can hugely accelerate the process.

That said, also read

* William Zinsser "How to write well". It's a very practical classic that improved my writing by a factor of two or more after one reading, and I found it enjoyable enough to read it more than once.

* Mark Forsyth "The Elements of Eloquence". Also highly enjoyable while remaining very practical (it also took several readings to remember a lot of the points he made, but it's reasonably short and each of the many sections are independent, so it's easy to open it up and learn something in 2-3 minutes).

If anyone is interested in the intersection of technology and writing eloquently, pull requests to https://github.com/sixhobbits/technical-writing/blob/master/... are very welcome