Definition of "collection" applied to a book collection

 Merriam Webster's Unabridged Dictionary defines collection, which includes (for book collecting purposes): 

col·lec·tion noun, often attributive \ kə-ˈlek-shən  \

inflected form(s): plural -s

2  : a number of objects or persons or a quantity of a substance that has been collected or has collected often according to some unifying principle or orderly arrangement: such as

a  : an assembly of objects or specimens for the purposes of education, research, or interest

<the magnificent collection of trees — Edmund Wilson>

 Origin of COLLECTION

Middle English collectioun, from Middle French collection, from Latin collection-, collectio, from collectus (past participle of colligere to collect, amass) + -ion-, -io -ion — more at COLLECT

“collection,” Merriam-Webster's Unabridged Dictionary, https://unabridged.merriam-webster.com/unabridged/collection. Accessed 2/26/2021.

(https://unabridged.merriam-webster.com/) $

How to tell a book's publication from it's copyright date

 New Media Rights, which provides legal services, educational resources, and public policy advocacy for creators, entrepreneurs, and internet users, explains the difference between a book publishing date and book copyright date.  For collectors, a book's copyright page is usually found on the verso of the title page.

... the copyright date that you see on the inside of the book jacket likely coincides with the date of formal registration or the date that the work was finished and submitted to the publisher.

The author of a work has a copyright to the work as soon as it is created. All s/he has to do is “fix the original work in a tangible medium of expression,” meaning either putting pen to paper or just saving a word document. 

An author can either retain their copyright, or assign it to a publishing company.

 (https://www.newmediarights.org/book/copyright_date_same_publication_date)

Do you have a pressed flower in your book? A letter? It's "ephemera"

 The Ephemera Society of America shares a long webpage on the term's definition with pictures and text covering a wide variety of ephemera.

Precious primary source information . . . that is what the ephemera world considers its bits and bobs of vintage (and current), usually paper items. Much of it was likely expected, back in its day, to be briefly useful then discarded. Today s auch items which have survived the vagaries of time often reveal things we might not otherwise ever learn.

 (https://www.ephemerasociety.org/definition/)