A good online resource is
http://www.tradecards.com/, run for the last 23 years by Ben Crane. There are a lot of articles on specific types of trade cards, illustrations of cards in various categories (under "Victorian Scrapbook"), and links other resources, including books about trade cards, most of which are out of print.
One of these books, "Victorian Trade Cards" by Dave Cheadle, was published in 1996 and is probably the best overview of and introduction to trade cards. Unfortunately, it's out of print, but you can find it online for about $30. Dave Cheadle has an eBay store, "Dave's Great Cards Galore", at
https://www.ebay.com/str/oldcardsatd...eatcardsgalore, where he sells trade cards and trade card resources. These don't include his 1996 book, but they do include a couple of his more specialized trade card books as well as back issues of "Advertising Trade Card Quarterly", which Dave co-edited for its entire 1994-2001 run. Dave also has a relatively new site, "Victorian Card Hub", which he launched a couple of years ago at
https://victoriancardhub.com/. It has some useful articles, including some that were originally published in ATCQ.
The late Ron Schieber compiled detailed checklists of many types of trade cards, including massive lists of thread cards and meat cards that have been invaluable in my own collecting. His widow Diana still sells these checklists, including a list of the lists that she might send you for free. Her e-mail is
diana.scheiber@gmail.com, and she's on eBay as madmoneyetc.
If you have any specific questions, I might be able to help. I've been collecting trade cards for the last 25+ years and have around 10,000 different ones, plus a pretty good reference library on trade cards and related paper ephemera.