I didn't even realize it, but after reading these posts above, I looked up Billy shelves on the Ikea website and discovered that the bookshelf I bought used from a newspaper ad 5 years ago is actually an Ikea Billy bookcase with glass doors - although mine has a gray or silver color finish, and the glass on the doors is heavily frosted so you can't see through them. US$169 on the Ikea website, and I bought mine used for I think $30, so it was still worth it. With those 11" deep shelves, I mainly use it to store all my oversized NIS America PE box sets and PonyCan releases, all my Studio Ghibli and other hardcover coffee-table-sized anime art books, and a few odd-shaped anime releases like lunchbox sets and larger DVD LE boxes and tins.
I built two new shelf units from scratch a few months ago, to add to the two units I constructed six years ago, so I had to move the Billy shelf upstairs into the living room to free-up enough space in my theater room for all four home-built 8-shelf units. Three of those four are now loaded up with anime, and the fourth with 3D movies, TV series, and Concert videos. I have enough live action Hollywood movies boxed up in storage to completely fill a fifth shelf unit, if I had one. I'm almost out of shelf space specifically reserved for anime already, so I may have to migrate some of my old DVD Box sets upstairs into the Billy as well. It's always a never-ending, vicious battle for shelf space, lol...