This site has been listed here before, but I'm going to "bump" it to be sure the new members at least get a look at it.
I DO RECOMMEND THIS SITE!
http://www.survivorlibrary.com/The files are all available for free download. It is predominantly PDF files.
PLUS
You may purchase a digital copy on USB flash drives or DVD / Blue Ray disks.
The size (presently) is about 165 GB...
[edit] I note a spelling curiosity which might help those looking for specific topics... The word "receipts" is sometimes used to indicate a formula or "recipe". While I would expect "receipts" to be an accounting term for business usage. Languages change over time and many of the references in this library (English language) are from over a century ago...
I note, for those interested, that the library includes a digital copy of "Culpepers Complete Herbal 1880" which is, still, a primary reference and well worth including in your library...