Calibre provides a very good service, but it can be a bit puzzling in terms of UX, also getting certain pirate books is a big chore and might require visiting dodgy sites. But the reason I stopped downloading books is that I often ran into small issues, like footnotes or a table of contents that didn't work correctly. The last book I remember downloading was "Thinking Fast and Slow"... I ended up purchasing it on Amazon because every half page it had a word duplicated, with the duplicate slightly scrambled srcambled. It was maddening... probably planted by the author , Daniel Kahneman, as a psy-ops DRM device.
They also provide an email address where, if you send an email with some epubs attached, they make them magically appear on your kindle.
I was pleasantly surprised by this last week, since I got a kindle and I thought it was going to be a hassle, but nope.
When I tried emailing an epub this way, Amazon messed up the conversion. I've had good luck converting pirated epubs to MOBI using an online converter so I haven't changed my practice.
I have an older Paperwhite; my GF has a newer one. I uploaded MOBIs to both last night (via USB) - it worked on hers, and they didn’t show on mine. I had to convert them to AZW3 and reupload for them to show in the listing.
(I’ve not checked, but it’s plausible my older model has more up-to-date firmware.)
Because of this support I can download directly from libgen without converting or using a different device. For books that are only available through Amazon, I have the Kindle app installed.
It remind me of whenever people discuss about OS and someone said their grandmother can use Linux just fine, hell, I'm quite sure she's just browsing with Firefox and not doing command line kung-fu.
If you use an Amazon account you can email them to a specific email address to get them on your device.
Download file > Add to Calibre > Transfer to Kindle
We're talking four clicks.