Any given English translation of Bible is by itself something like 3-5 megabytes of ASCII; the complete works of Shakespeare are about 5 megabytes; and I think (back of the envelope estimate) you'd get about the same again for what Arthur Conan Doyle wrote before 1900.
I can just about believe there might have been only ten thousand Bible-or-Shakespeare sized books (plus all the court documents, newspapers, etc. that add up to that) worldwide by 1900, but not ten.
Edit: I forgot about encyclopaedias, by 1900 the Encyclopædia Britannica was almost certainly more than 50 MB all by itself.