I've also, unfortunately, had to begin storing some books horizontally on top of other shelves of books. Not ideal, I know, especially for the books underneath, but at least these are fairly light. Over the past couple days I've been trying to gather up all my older Hale novels and fit them into this cabinet, since they're all the same size, and two shelves' worth fit inside perfectly - I can still get the doors closed without major hassles. But eventually all the fuzzy-wuzzies and beanie babies on the top shelf will have to vacate, in favor of more books.
This has opened up some space on the shelves downstairs, but it doesn't solve the overall storage issue. I've detected one space downstairs where another stack of shelves just might fit (in my husband's office), but it may be time to ruthlessly weed my collection, picking out books I know I'll never read and donating them to the library and/or annual book sale. I'm not sure why I feel the need to keep so many around the house when I work in a building with a million volumes, plus ready access to interlibrary loan. It's a problem. Not sure exactly what to do to solve it, though.
p.s. Happy Bastille Day, everyone. Anyone else ever listened to the lyrics of La Marseillaise? Talk about bloody imagery. The Star Spangled Banner is pretty tame in comparison. "Qu'un sang impur abreuve nos sillons" - indeed. In 9th grade French class, we really didn't know what we were singing about, I realize now.