We purchased two of these Billy-style bookshelves in black-brown from IKEA for use in my booksales business. The bookshelves require assembly, but are fairly easy to assemble. They are made of chip-board which is covered with a real wood veneer. The price was the absolute best I was able to find anywhere for similar shelves.
My husband did have some trouble assembling one of the units. It broke in the middle where the stationary shelf goes. Other than that, we have not had a problem with the units.
The IKEA Billy bookshelves in black-brown are sturdy and attractive. They even come with an anti-tip bracket to attach them to the wall. You wouldn't know just by looking at them that they were made of particle board; they look like real wood. They are lighter weight than most particle board shelves, which for us, was an absolute must.