Instruction: Given a question and the related document, and generate the answer to the question based on the information provided in the document.

Input:
Question: How much weight is each shelf rated for? I feel like stacking them heavily with books may be a bit much for the flimsy thin shelves.
Document: The contraption is quite sturdy for its low weight.If you load it down with heavy books, you need to pack them from edge-to-edge to keep them from tipping, although this may be a problem of carpeting or uneven flooring, although I doubt it. The shelves hook over the tubular steel used to construct the cross-braces for the shelves, but are slightly (maybe three-quarters of an inch, or an inch - half an inch per side) less wide than the frame, so if one puts a very thin book (many books of philosophy, etc.)
There was a visual difference in the size of the tube runners that hold the the two sides together and the shelves felt almost paper thin. Don't know if they decided to cut material costs to keep it the same price or make more money but I am much less confident in the 2nd one I received lasting as long or holding as much weight.
Packaging was good. Very easy for one person to assemble without instruction sheet in no more than a quarter-hour, although smaller people may have need to two persons to assemble it. Includes all screws (although no extras, so if you strip one, you're screwed); the screws are hex, and a small hex wrench is included, the only tool needed to assemble. Tubular anodised or powder coated steel construction, with perforated steel shelves.The shelves bend a bit under load (I have it loaded with 40-55 lbs per shelf, about a dozen large hardcover textbooks and hardcover and leather-bound books of religion, per shelf, no paperbacks - or at least not any paperbacks that weigh less than 3 lbs - and anyone who has ever had a library full of texts on physics, chemistry, and Christianity can attest the books aren't octavo-sized miniatures: religious books - and most textbooks - are bound larger than life) but appear sturdy - the fact that it's holding up under 200 lbs or more of books proves that.
Easy assembly. Very light weight. Back bars keep it from being terribly flimsy. It is fine for books but not as ask nick knack shelf
I like these book racks so much, I'm going to order two more. They came packaged well, every piece was wrapped separately. They are very easy to put together and sturdy when finished. I placed one in my kitchen to hold all my cookbooks and still had room to display decorative serving platters. The other one is in my office and is full of large textbooks and reference material for my therapy practice. Even with all that weight, the shelves do NOT sag. I'm very happy with my purchase.
The shelf is made from a thin but sturdy metal that works well for holding almost anything on the shelf. It's easy to assemble too as there's only one type of screw and even without directions is easy enough to put together. The downside is because the metal is thin for the shelves, they can get bent during transport as two of my shelves were dented on the sides. It made the rods fit more snugly due to the distortion, but it still worked, so be aware that you may get dented shelves. The other issue that lowered my rating for this item is it was missing a screw, so I couldn't put one of the bar up at the top.
towards the edge without pressure from the stack of books against the frame, it can fall through the small crack.Overall, it's relatively large, relatively cheap, metal, and sturdy enough to hold scores of large, thick hardcover tomes of several pounds each, which most of the particle-board cases aren't, as they bend - and eventually break - under the weight, due to the nature of particle board. It's enough to hold ~70 textbook-sized A4 or 12 by 9 inch hardbacks arranged vertically, about ~100-110 trade paperbacks or mass market paperbacks of non-enormous length arranged vertically, and some ~150 paperbacks stacked horizontally, or double that (although I do not know if it could support the weight) if they're stacked two-deep.Overall, I give a 8.5 out of ten, or four and one-quarter stars, and recommend it with some small reservations as mentioned above (mainly the books falling through the edges of the shelves if they're thin) but you're not going to find any shelf without those reservations until you get in to the solid-steel institutional-quality bookshelves in the $500+ range, or solid wood bookshelves that are very heavy and don't hold as many books in a similar price range.Five stars out of five for the price, which for me was ~$75 with free shipping from Amazon.Edited 07/06/11 to more accurately reflect the greater weight of books the shelf now bears admirably.
It's a perfect fit for the space I had available. I'm using it as pantry-type storage, free-standing in the kitchen of my new pantry-less apartment (in school, living on a student's budget). I was going to go with one of those wire-rack storage shelf systems, but they're all about 36&#34; wide, and that didn't work for me.Assembly instructions could have been a bit better, but they weren't really necessary.The shelves are sturdy enough, but anything somewhat heavy (like a 2L bottle of soda) in the middle of the shelves that isn't big enough to rest over the support bars at the perimeter will cause the shelves to bow a little.Overall: Happy with the purchase.
This metal rack is a great option. I love it so much I've purchased several and they not only look great (better than the picture), they hold a lot of books, even my heavy text books and practice manuals from my massage therapy practice. Books are heavy but the shelves in this rack appear to hold their accumulated weight without sagging.This rack is practical and versatile as well and can be utilzed for many things other than your books. A quick scan of all the other 5-star reviews will tell you how it has been put to great use in home offices, the kids' rooms, the dorm, the garage, the kitchen, even closets.
It is rather lovely in it's simplicity, and is very sturdy. Also, this was my first time assembling something like this, but it was still very easy - it was mostly just screwing the pieces together with the included Allen wrench, and the shelves snap on over the metal bars.I have a bunch of heavy books on it with no sign of problems. It did seem wobbly on carpet initially, but the added weight of my books leaves me with no worries of it falling over.Love it!!!
Answer: I have 5 units now - one 3-tier, four 5-tier - from 2 different suppliers.  I have them crammed with books.  No problem.  They are metal and very sturdy.  I cannot find a specification for weight per shelf.