His collections of letters and journalistic work is way better than his books. He always hated writing books and was much better in short brilliant bursts. He wrote extensively to his friends (some very famous friends like Tom Wolfe and other great writers).

Both the letters and articles were released in 3 book series each. These are my favourite books from each series:

(letters) The Proud Highway: Saga of a Desperate Southern Gentleman, 1955-1967 (The Fear and Loathing Letters, Vol. 1

https://www.amazon.com/Proud-Highway-Desperate-Gentleman-195...

(articles) The Great Shark Hunt: Strange Tales from a Strange Time

https://www.amazon.com/Great-Shark-Hunt-Strange-Tales/dp/074...

HST's fiction and even most non-fiction journalism was never as good as his letters to his friends (his friends included famous Beat writers and 1960s literary legends). His writing quality follow this hierarchy:

Letters -> Journalism -> Fiction

Largely due to his inability to focus on long works due to his (hilariously) reckless lifestyle. He was brilliant in small short pieces. I learned this having read nearly all of his work over the last 5 years. I recommend his collection of letters, published across a 3 book series, which he preserved over the years from being teenager in the 1950s to becoming a famous journalist in the late 60s.

http://www.amazon.com/The-Proud-Highway-Desperate-Gentleman/...

For example one of his letters that went viral recently, written while he was 20:

http://www.brainpickings.org/index.php/2013/11/04/hunter-s-t...