Thanks to a post at the amazing BibliOdyssey, I came across the recently-launched World Digital Library. Though still a work in progress, it's an amazing collection of books, manuscripts, maps, photographs, paintings and other oddments from all over the world. All can be viewed online or downloaded as images or PDFs.
It has a couple of sections of particular interest to bookish types: the literature collection and the books collection (some overlap there). There are some beautiful things to be found there, including all 54 volumes of a 17th-Century woodblock-printed edition of The Tale of Genji (plus six volumes of supporting information). Here, for example, are the cover an an internal page from volume 16.
Then there's Soga's Robes, which hasn't much of a cover, but does have innards like this:
Or perhaps you'd prefer the Chinese Annals of Creation?
Or a 19th-Century Russian manual explaining to Russian peasants how to go about resettling in Siberia?
There's a heap of other stuff, including William Blake, a 15th-Century Aesop's Fables and Edmund Dulac illustrating Hans Christian Andersen.
I'll leave you, though, with the beautiful covers for the 20 volumes of Takizawa Bakin's Nansō Satomi Hakkenden.