I’ll stick to the big 3 here, but please let me know if there are other publishers you are curious about.

1. Elsevier books are purchased by copyright year (paid from er14) and includes all titles except “medical” items not sold under this model, major reference works, and textbooks which are offered to us on a title by title basis (they send me a picklist every year). We also buy Elsevier book series and I believe that order is still split among the funds that originally purchased the print.
2. Wiley books are purchased by copyright year (paid via er14) and follow a similar model meaning we get everything that isn’t a “textbook” – those can frequently be purchased via Ebsco or Proquest, and Major reference works. And we buy reference from a picklist like Elsevier.
3. Springer is the hard one. It is used to be everything, but when they merged with Palgrave Macmillian (who owns Nature) it became more complicated as they added Palgrave, created new packages and upset the apple cart. What we don’t get from Springer now are the following packages:

Springer doesn’t sell title by title themselves so Ebcso and Proquest maybe the only avenue for this content, if they are even able to get it from Springer.

Willy updates records for these collections on a regular basis so searching the opac is one avenue to figure out what we are getting. Another is to search the platform of a specific publisher and see if an items is working, however, I caution this approach with Springer as they tend to turn on “trials” that we don’t know about.  L  And, you can always ask me about a title. The science selectors frequently do.