There are two ways to answer that. First to mention writers who wrote like Bukowski, influenced him or dealt with similar subject matter. Then there are the authors who were completely different stylistically and whom he sometimes even slagged off publicly, but you find fringe "counterculture" people who are into Buk often appreciate. You can't go wrong with Mailer and especially Henry Miller, probably my favorite author. Mailer is too Harvard intellectual and Miller too philsophical and romantic for B., but they fit the bill if you're looking for some old fashioned hardboiled masculine firepower. Burroughs and Robert Anton Wilson if you're into drugs and head trips. Strangely the guys Bukowski probably has the most in common with are the old Zen/Taoist Chinese and Japanese poets. We know he dug Li Po. Also check out Han Shan, Ryokan, Ikkyu and Issan. A lot of similarities: Simplicity, earthiness, melancholy, the hermit hiding from the world perspective, and of course the love of Wine. In a way Bukowski was very Zen, even if he would never admit it. There's a great anthology called "The Poetry of Zen" that I recommend if you're into that sort of thing.