So my wedding is coming up this year, and she and I are exchanging gifts. She's a librarian. Books are her life. she spends almost all her extra disposable income on books. but her bookshelves are kind of wobbly and don't hold much.

I want to get her a proper heavy-duty, large-scale book-shelf. Something that can withstand a few hundred lbs without bowing and be stable and look nice. It doesn't have to be made out of ebony or mahogany and weight 2000 lbs, or look like something from the middle ages. the budget is about 500-600. What kind of price am I looking at for a upper-middle class bookshelf that isn't too crazy or looks like modern art? and where can i find such a thing?