Maintaining the metadata for your books can be quite a chore. Joel Friedlander's overview covers some of the basics.
It takes me two pages of my multi-page management spreadsheet to hold the simple columnar data (ISBNs, Library of Congress (LoC) numbers, publication dates, page counts, etc.) and textual data (blurbs in various lengths, keywords, BISAC codes, etc.). Some of that data is static, but parts of it are changeable based on marketing experiments, temporary sales, and so forth.
When we go to a distributor site that caters to indies, we are usually presented with a form to fill out for each book. Since I strive for consistency, I always have to open up the form for a book I've already posted to that distributor, to make sure I fill out all the questions the same way across all my titles.
How do the big boys handle this?
Well, that's a question, isn't it? It's hard to get the details. The big traditional publishers have complex internal needs (moving a title from acquisition through edit, formatting, marketing, publication) involving different departments and requirements, and their management systems are crafted with that in mind to give them a shareable single complex record for the title that holds both in-house private data and public data intended for use with their trading partners (distributors, retailers, etc.)
The output of their systems these days tends to be in the form of ONIX records (see below) — this much I know. But exactly how they share those records with their partners is obscure to me. (Alas, trad-published authors who've added indie-publishing share insights with us, but we don't meet a lot of back-office technical types from the traditional publishing firms.) You can see how vague the specific details are for an overview on metadata maintenance that's meant to be helpful, or for a discussion about refreshing metadata as things change.
The big traditional publishers have much more complicated problems. As indies or micro-publishers, we get to choose what we want to deal with, and some of the industry tools are available for us to use, if we think it's important enough.