I love bookcases. When I decided to convert my spare bedroom into an office I had three bookcases made to fit into the built-in wardrobe (almost floor to ceiling). I had a smaller one made to fit under the window and a double-sided one on wheels made so I could pull it over to my desk and pick books from it as I worked. They're gorgeous. When I moved house, I had the bookcases pulled out and brought them with me. This office (another spare bedroom) is a different size and shape but I've managed to fit two of the bookcases into the built-in wardrobe and the rest around the room.
My only problem is the bookcases are over-full. I suspect it wouldn't matter how many bookcases I had, there'd always be more books than shelves. I spent all day today tidying one bookcase. Before I moved I had all my fiction books sorted alphabetically by author and my non-fiction by subject and then alphabetically by title. The system was brilliant. I've been studying since I moved here and haven't sorted my books yet. Having one bookcase sorted doesn't really mean much in the scheme of things. It's one of the fiction cases and, while it's not yet in alphabetical order, I do have all the books by one author together. That way when I get around to doing the alphabetical bit I won't have to search all over the room for each author.
It's exciting. I can look up now and see a whole shelf of Asimov, another of Eddings and Irvine and Dart-Thornton. Still another has Kevin J Anderson and W A Harbinson and Matthew Reilly. Whenever I'm looking for a book by any of those authors I'll know exactly where to find it. Only two large and three smaller bookcases to go. At least the fiction and non-fiction is already separated. That makes it easier. The non-fiction is also already arranged by subject, except for a couple of books that haven't been put away yet.
Having books easier to find makes it easier for me to read exactly what I want as well as making research easier. With all my gardening and herbal law books together and near all my medieval history books, I can find just about anything I need for my current w-i-ps. They're all just behind me too, so I can roll my chair back, grab a book and roll back to the computer, all in just a couple of seconds. I love being able to use things efficiently.