Last year I got into using Letterboxd, to complement my goal of watching more (good) movies. It’s got a really clean interface, the social features are useful but unobtrusive, and it makes remembering what I’ve watched and when I watched it easy. So why isn’t there a Letterboxd for books?

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Building a Letterboxd-style book tracking app turns out to be surprisingly hard due to the ISBN problem. Unlike movies, books have dozens of ISBNs per title (one per edition, format, and printing), making search results messy and unusable for casual logging. The FRBR model used by librarians distinguishes between works, expressions, manifestations, and items — but most public APIs like Google Books return low-level edition data rather than canonical works. OpenLibrary is the closest open alternative but has data quality issues and 40+ million entries with duplicates. No clean, open, high-quality book database analogous to The Movie Database exists, making the project significantly harder than building a movie tracker.

The Perils of ISBN