We genrefied our fiction collection a few years back. We are a 9-12 high school of about 900 students. I don't regret doing it but it is absolutely an imperfect process.
How long will it take? The physical moving of books and updating the catalog is doable for a single person over the course of, say, a week. If they know what they're doing it can go pretty fast. The harder part is choosing the genres. We, as librarians, needed to identify the genres; then our clerk did the physical moving work over the summer. Genres are frequently not cut and dry. Is it dystopia or action? Is it mystery or realistic fiction? If it was a book published in 1980 about a story set in 1980, is it historical fiction or realistic fiction?
We kept the call numbers the same but changed the publication of the book in Follett. The genres we used in the end (not that this is ideal - just the best we could do at the time):
- action / adventure
- historical fiction
- humor (later deleted)
- mystery / horror
- realistic fiction
- romance
- sci-fi / dystopia / fantasy
- sports (thinking of removing)
Each genre has a color. The color label covers the call number on the spine and matching colored signs above the shelves indicate what section they are in.
Many kids really like this when they're browsing. It leads to hiccups sometimes. If a kid asks me where Divergent is I know it's by Veronica Roth but do I remember the genre? (turns out I put that in action/adventure instead of sci-fi/dystopia because the sci/fi dystopia section is MASSIVE - so not always cut and dry)
I'd say you could start picking away at it by adding sublocations in the catalogs now. Or just physically tagging or stacking the books by genres. That way the physical movement can happen over the summer.
And it's ongoing. We just found The Monstrumologist in realistic fiction. Pretty clearly horror. Sometimes the book description alone isn't enough to determine its genre. So every new book that gets added needs a determination.
I hope that helps. At least a little. I don't think we mastered a system for doing it - but we did manage it so... that's something!