Came across this article by Paula Findlen in a recent Chronicle of Higher Education. An interesting point I’ve never thought about, how the digitization of all these pre-1923 works could help inform scholarship. Books with a 19th century publishing date are generally relegated to off-site storage (cue ominous music and lightning flashing behind some imposing edifice). Digitization has brought these books to the forefront and made them searchable. Ms. Findlen describes how reading such texts from her research period has informed her research. Nothing like reading something written in a specific time frame to give you a flavor for the time.
Project Gutenberg is a great place to find such titles. You might even find a book whose content has been made available for an eReader.