Despite my best efforts at organizing

I cannot find a book I know I own.

I know I own it, because it's listed on Library Thing, and I only very rarely lend books out. So I know it's in my house... somewhere.

Problem is, I can't find it.

That probably means I own too many books, or don't have a good system for organizing them. I've been thinking I could include Library Thing tags that indicate what shelf the book is on, but the thing is, the location of my books changes periodically, depending on what I'm working on at the time.

Most of my books are kept in the spare room/library. That's always the first place to look, and everything is arranged by genre or topic, and then alphabetically. So, for example, all the literary theory is together, all the medieval lit, and then all the novels are arranged by author in alphabetical order. So I usually only spend a moment locating a given text.

There is also a bookshelf in the living room, but those books don't change much. I've also got a shelf on my night-table filled with books, but those are almost always fiction and usually consist of books I want to read soon.

Then there's the office/study. There are a few shelves here, and these are the books that most often change, because I bring things up from the spare room as I need them for whatever project I'm working on. Because of this, they tend to only be loosely arranged by genre or topic, so I have to spend a little time looking through these shelves. Luckily they're small enough it doesn't take long.

Thing is, there's this book I really want to check out for the chapter I'm writing right now, but I've been through my office shelves twice and can't find it. I purchased it specifically for the dissertation, so it should be here. But it's not.

I know it's in my house. I just need to figure out where! Then maybe I need a new system...