Your PDFs and EPUBs, reading each other.
Happybook turns a pile of PDFs and EPUBs into a notebook: highlight the passages that matter and draw links between documents, so page 12 of one paper can point straight at the figure that answers it in another.
Open Happybook Free, works offline, no account needed. Sign in with a passkey to sync.Notebooks of documents
Drop in a PDF or EPUB to start a notebook, then keep adding sources as the project grows.
Cross-links
Select a passage, link it to a spot in any other document, and jump between the two in either direction.
Offline first
Documents and notes live on your device. Airplane mode is a reading room, not an error page.
E-reader ready
Every account is an OPDS catalog: browse your notebooks and download their books in KOReader or any OPDS reader. Reading progress syncs both ways, so the device and the web reader stay on the same page.