Ikea is not high quality compared to most gallery-style furniture. If you're buying flat-pack furniture to assemble at home few brands will serve you better.
Oddly enough, none of my bookcases in my new house are Billy ones though. Yes, I still have loads of physical books. I found a Chinese brand of all-metal bookcases that are lighter weight than Hon or Steelcase but hold a lot more weight than Ikea bookcases of similar price. They don't suffer from the famous bowed shelf problem most MDF shelves get. They're also packed flat. They even disassemble and reassemble neatly for moving or storage. It's Oseillc, which is a brand of Outstar Office Solutions, Ltd. They also make a little institutional, industrial, shop, and retail furniture under the parent company's own brand.