Morgen Gebether. German Manuscript Book of Prayer, 1782, Germany. This manuscript is the perfect example of “never judge a book by its cover”, with such a plain binding. Absolutely floored by the calligraphical work. [1440×1800]

For context, the binding is an unassuming plain black cloth, an obvious rebinding, but so boring for the contents.

I had a similar one from 1668, but sold it on ebay. I like books, but these religious works are not enjoyable, except if they would contain miniatures (but then we talk about a very different price class).