You might check out this extremely detailed write-up from Andrew O'Hagan, the author who was hired to ghost-write Assange's autobiography, and wound up hanging around his inner circle for some months. It's a pretty sympathetic account, but it's hard to come away from it sympathetic to the man. While O'Hagan praises Assange's ideals and seems to like him personally, he doesn't gloss over his flaws, and the portrait he paints is ultimately of a supremely self-interested guy who spends much of his time scheming against his closest allies and lying to pretty much everyone.
One exchange that stuck in my mind:
> There are few subjects on which Julian would be reluctant to take what you might call a paternalistic position, but over Snowden, whom he’s never met but has chatted with and feels largely responsible for, he expressed a kind of irritable admiration. ‘Just how good is he?’ I asked.
> ‘He’s number nine,’ he said.
> ‘In the world? Among computer hackers? And where are you?’
> ‘I’m number three.’