Project Gutenberg is a top choice. It has over 60,000 free e - books, and a large portion are novels. It's been around for a long time and is very reliable. Another one is Wattpad, which is popular among young adults. There are a lot of emerging writers sharing their stories there for free.
Websites like KissManga and MangaFox are often used. They offer a large collection and are user-friendly. However, be aware of potential ads and the legality of some content.
Project Gutenberg is excellent. It has a vast collection of classic literature, and there are some classic thriller - like works there. Another is ManyBooks.net. It categorizes books well, making it easy to find thrillers. And Free - eBooks.net also has a decent selection of free thriller novels.
Comixology has a free section where you can find some really interesting graphic novels. They often have promotional offers for free reads. Another good one is Tapas, which features a large number of graphic novels in different categories, and many of them are free to read.
Wattpad is very popular. It has a huge community of writers and readers, so you can find all kinds of novels there, from romance to science fiction. Another good one is Scribd, which has a large library of e - books and novels, though it requires a subscription for full access.