Oh, absolutely — integration is not only possible, it's something I geek out about whenever I think of book apps. I’ve played around with a few pet projects and helped a friend prototype a reading tracker, so I can picture the whole pipeline pretty clearly.
First, Goodreads: historically they offered a public API that lets apps read a user’s shelves, get book metadata, and pull reviews, but it comes with caveats — keys, rate limits, and sometimes limited write access. A very pragmatic path I use is to let users connect their Goodreads account (via whatever auth flow is available) to import shelves and ratings, or offer a simple CSV import/export fallback because Goodreads lets you export your shelves. That solves a lot of immediate friction. For richer metadata and cover art, I layer in other sources like Open Library, Google Books API, or WorldCat to fill gaps and normalize editions — ISBN matching plus fuzzy-title algorithms help de-dup multiple editions.
Libraries are a whole other, delightful beast. Public library systems expose data through multiple channels: some provide modern REST APIs (OverDrive/Libby partnerships for ebook availability, OCLC/WorldCat for catalog search), while many still rely on traditional protocols like Z39.50, SRU/SRW, SIP2 or NCIP for circulation and hold requests. If your app just wants to show availability and links to the catalog (OPAC), the simplest route is using library-provided APIs or Open Library/WorldCat lookups and deep links to the local record. If you want to place holds or check out items, you'll need to integrate with the library’s authentication (often via library card and PIN) or go through vendor partnerships (OverDrive requires agreements to borrow ebooks). Practically, I build a backend microservice that handles sync jobs, caches availability for a short TTL to avoid hammering APIs, and transforms different metadata schemas into one canonical book object.
Two non-technical things I always insist on: privacy and UX. Let users opt in to what gets synced, explain where credentials are stored, and keep sync controls obvious. Also plan for mismatch handling — editions, missing covers, or library branches with different holdings — and show helpful fallback actions (suggest interlibrary loan, show nearest branches, or let users request an item). Starting small — import shelves via CSV/Goodreads, show local availability via WorldCat/Open Library, and then add borrow/hold features as agreements and authentication allow — kept my prototypes ship-shape and made users actually use the feature. If you want, I can sketch a minimal API flow next time or suggest concrete libraries and endpoints I liked working with.