Overall, these bookshelves are really beautiful and sturdy. They look great, and feel very sturdy! They far exceed the quality I would expect for the price!The shelves are fixed sizes, but both the 3- and 5-shelf version have relatively larger and smaller shelves that can fit a wide variety of books of all sizes.Assembly is very easy but time consuming. The instructions are clear, everything is labeled well, and it's basically impossible to mess up assembly. The vast majority of assembly is cam-and-lock, with a few screws that have pre-drilled holes. That said, it takes about two hours per bookcase to assemble (and after assembling three in a row, my thumbs were thoroughly blistered over from all the screw-tightening!). Note: these bookcases include more spare parts than indicated! I freaked out after assembling my first one when I had 3 spare dowel pegs instead of 2... but then later found out that all bookcases I assembled had more extra parts than indicated in the instructions.Overall, construction and engineering on these bookcases is solid. The finish is textured (i.e., it's not just a flat finish, but there are actually grooves you can feel where the "rings" in the wood are). I also appreciate that the back of the bookcase is study plywood that gets screwed into every. single. shelf. (whereas some competitor products are just cardboard backing that easily rips and does not support book weight). The decorative flourishes, including baseboard moulding (and crown moulding on the 5-shelf bookcases) are really nice.These bookcases DO need some very minor customization to be perfect. First, as pictured, it's pretty common for parts to have minor imperfections. These can be fixed with a nice wood finish stain marker (I used a dark walnut stain marker and it fixed basically all imperfections in the wood).Second, the cam locks do not have covers (and thus there are bright silver shiny cam locks visible inside each shelf). I bought some black cam lock covers off Garvee, which make this furniture look amazing!As a final note, the tall 5-shelf bookcases naturally lean backward (the 3-shelf version does not do this). So, the 5-shelf bookcases are only appropriate where they can lean against a wall. Otherwise, the 3- and 5-shelf version of this bookcase are perfectly aligned and can be mixed and matched as desired for whatever interior design you're going for!So, if you want these fantastic bookshelves, just plan on spending an additional $20 on a wood-finish stain marker (available on Garvee) and some black cam lock covers (also available on Garvee).