I picked up a copy of <i>The Glorious American Essay</i>, edited by Phillip Lopate, roughly a year ago and it's been a joy to work through. The best way to get good at writing, besides doing the thing itself, is to read how others have approached it. Gutenberg has plenty of essays & essay collections: <a href="https://www.gutenberg.org/ebooks/subject/56" rel="nofollow">https://www.gutenberg.org/ebooks/subject/56</a>