Of course the press are mostly talking about your data being used to target pharmaceuticals and the such like… or worse.
But do you really want your ISP potentially selling data that includes fanfic you read?
I am pretty sure it’s a no.
But here’s two things:
A lot of Tumblr sites don’t have SSL (https) enabled, even though it’ll reduce the detail of data available to ISPs when people visit a site (the Tumblr dashboard is, however, served over SSL)
AO3 (Archive Of Our Own) doesn’t have SSL (https) (though they do want it and if you know anything about puting https on a site, I know they’d love to talk to you)
So how do you improve your privacy when it comes to reading fanfic? (also when you’re uploading on AO3)
Sign up to a VPN service that’s availble on PC and mobile (I use Tunnelbear, but there’s a lot of paid ones out there, just don’t go for a free one, as they tend to be very dodgy)
These aren’t fullproof options, but will go some of the way to keeping your online habits private.
*Due to our own legal BS here in the UK (the upcoming IP Act), this advice should also be followed by my fellow UK peeps, because you never know what our government will make illegal next.