I don't think the news that Mein Kampf is an e-book bestseller is necessarily a cause for alarm. Vocativ's Chris Faraone is probably right to say that the anonymity of e-readers has led to a sudden burst of interest in Hitler's book, the same way that e-books led to Fifty Shades of Grey's success. But I don't think we're going to see increased attention in Nazism because these books are suddenly selling again.
Let me explain: One of the first things I bought in a bookstore with my own money was a copy of the Satanic Bible. I was a kid, and the Waldenbooks at the Maine Mall had a copy in stock, and I was curious, so I bought it. So transgressive of me! I started reading it and soon realized that rather than the chamber of hidden secrets I wanted it to be, the book was just the kooky ramblings of a pissed-off old guy. I abandoned the Satanic Bible pretty quickly.
I suspect that Mein Kampf is selling to ignorant-but-curious people—a combination of idiotic jerks like teenaged me and the idiotic attention-cravers you find on 4Chan—who expect the book to be full of all sorts of crazy bullshit. I can't imagine these buyers of Mein Kampf will hold on through the stultifying autobiography that the book actually is. Mein Kampf isn't going to start any political movements these days. It isn't really any good for anything anymore besides shocking people with the simple fact that it's Mein Kampf. Mein Kampf making waves on e-book bestseller charts is like some asshole leaving a bunch of swastikas in a comment thread: Vaguely shocking, but mostly a reminder that the world is full of stupid people.