I have bought a couple of these bookshelves in the past and they have been great. I just bought this new one for our baby room to hold all the books we will be collecting.
Even with my big belly in the way, this bookshelf is very easy to assemble. All the pieces are labeled and they give you extra little parts in case you lose or break something. The manual is simple to follow with pictures, but does not give you much detailed instruction.
The boards are made from pressed wood, but all the holes are pre-drilled for easy assembly. Each shelf sys it can hold up to 50 pounds. I'm sure I have gone over this weight limit with all my college books though. I have never had a problem with the shelves bending or giving way.
The only thing I wish was different is the backing of the shelves. It is just a thin cardboard flap that gets folded in 3 for packing in the box. If you're not careful when stretching it out and nailing it down, you can rip the back along a crease. It would also be very easy for a book to be pushed too hard against it and possibly make a hole in the back.