Based on a quick look, the biggest features it has that browser bookmark managers generally don’t have is the ability to search within saved webpages and documents without opening them. Plus, you can share bookmark collections with other people. Sounds a bit like a modern rendition of del.icio.us
+1 for ReadEra! Besides .pdfs, it covers a lot of ebook file formats, like .epub, .mobi, .azw3, etc. I typically download .epubs because you can change the font and font size, as well as use dark mode quite easily that way. And it looks like the most recent update now has TTS available for Premium users. It’s a very solid app, and is my top choice as well