Anna’s archive https://annas-archive.org

Library genesis https://libgenesis.net

Project Gutenberg https://www.gutenberg.org

Depends on region… depends on what you want to read… depends on you e-reader.

For example a kobo or a kindle will only read from kobo and amazon respectively.

Kobo and Google Play Books is my first stop to shop, since it supports Adobe Digital Editions, along with their own apps.

Amazon is my second stop. Not because I like them, I’m I. The same boat as you. But believe it or not their encryption is based off of your devices serial number. And you can DeDRM your Kindle books very easily.

Then it’s from publishers directly if they let you, like J-Novel Club is pricy but they offer drm free books.

My last option is obscure, but cool if you are looking for a deal. Humble Bundle is where I go for textbooks and older series. Only issue is they sell only in Bundles, and you’d get a lot of stuff you may not necessarily want. But the deals are crazy if you don’t want to pirate.

Finally depending on value and how much I feel the book is worth, I may sail the high seas.

Usenet

Library Genesis.

While you’re mainly looking for sources of new books, since you’re a fan of Fantasy and Sci-fi, I’d like to mention Luminist.org, which has the most complete archive of classic fantasy & sf fiction magazines and pulps available for free!

Its so complete that it is entirely overwhelming where to start. Personally I would suggest Galaxy, Fantasy & Science Fiction, IF, Destinies, Analog, and Asimov’s

Libby/Overdrive for ‘borrowing’ getting ebooks form your local Library. The Internet Archive is another good free source. When they aren’t being attacked by publishers and hackers anyway.

As many users mentioned all shadow libraries, but also Google just search for the title with type:pdf or epub and have direct links to that book. Ex: harry Potter type:pdf

Libgen is correct answer

My library’s app will install them remotely via overdrive. If it’s not on there, Usenet works as well as anything else.

Also a friendly reminder to support your local library. Many libraries offer digital and audio books now that you can download! All for free!

Ebooks.com often sells drm-free ebooks, depending on if the publisher allows it

If you want another marketplace to buy books that isn’t tried to Amazon try Kobo

Honorable mention must be made of Anna’s Archive. It’s a little slow, but you can probably download the books faster than you can read them.

When you get tired of trying to pay for it and realise if they don’t want to make it easy for you to purchase then you should pirate it then check out myanonamouse :)

Bookshop.org is a great spot. Directs money to small independent book stores from your purchase and you can even choose which book store gets the money.