[Idea Validation] Your library (ebooks) online.

An online webapp (and later apps on iOS and Android) to upload your books (PDF, epub, azw) and have them synced.

• Read your books PDF/epubs online, highlight, annotate- synced across devices.
• Quick search through names, tags (that you give your books) or notes.

I read a lot of books and most of them are in PDF or epub and I read in quite non-linear fashion. I don't have more than 300 books but they are all here and there and there are multiple formats (and hence multiple apps on different) devices. I have looked into all the available option, but nothing seems to be targetted for 'online custom library for a lifetime'. Now I want to make something for myself, and was curious if someone thinks it's something that could be converted into a indiehacker project.

Online means, synced across devices (initially a webapp)
Custom means, it's your PDF, ebooks, and you upload them and title or categorize them.
Lifetime means, they stick with you and it has actual library kind of feeling since you categorize and curate your own collection by uploading files on your own.