You can get little plainer picture book/rack tables like the loud giraffey ones, from - do not laugh - library suppliers such as the mighty Gresswells.
It helps if you are a fan of Ikea-ish blond laminate looks though. Not much call for solid French oak etc in your standard children's library.
I can't do you a linky pruni as Gresswell's site is a car crash as far as frames are concerned.
But have a browse and a jolly good laugh at some of the other products on sale!
oh dear god..loads! about 10 ladybirds ones in botom sling, 6 bigger ones in next up, 10 thinner ones next then 5 very big(dora/scooby) books in top, plus big musical winnie the pooh one, 5 thick card ones under bottom sling, then 10 under bottom shelf, stacked tidyly so you can pull them out easilly!..and no im not super efficient or tidy, it took me a while to merchandize!..but still plenty of space to see whats there
We have a fab one from http://www.tidy-books.com/ (sorry still haven't sussed out how to link). It comes in wood or cream finish, with or without alphabet letters and holds around 85 books. We bought one in plain cream with no letters as, like you, I prefer storage which is not too babyish/garish. It is v slimline and take up v little space. My DS loves it as he can now see all his books and pick our his favourites by looking at the covers.
Yes it does cost more but you can also use it for older children to hold CDs/DVDs, esp if you get the plain version. Jojomamanbebe also sell it (in plain cream), for a bit less (£99) plus you can use the mumsnet discount to get 10% off. I think its worth it having bought one...