Natural Pine Bookcases from BiGDUG are great value and incredibly easy to assemble with all necessary parts supplied in a single kit.
Overall these are just what I needed to store a large number of books. Only 2 minor niggles -
1. Both packs I purchased did not have enough screws in them. Fortunately I did already have some similar screws I could use to finish the job.
2. The shelf height could have been about 10mm higher so that it could accommodate some of the larger books. Only a few, mind, so not a major problem.