This is a very solid piece of cat furniture - as it should be, for the price. Fortunately, my cats love it and happily hang out on all levels. The cat tree took well over an hour to assemble. At times the instructions took a few extra reviews to understand exactly what needed to happen next, but I appreciated the "key" for all of the hardware, which helped a lot. Generally, it's not difficult but IS very time-consuming to put this together as the tree comes in so very many pieces (17 wooden pieces, 3 sisal pads, 2 pads for the base of the tree, and dozens of screws, washers, wooden pegs, etc.) It was nice of the manufacturer to include both a screwdriver and a packet of extra hardware. 

I strongly recommend having a second person available to hold pieces steady - particularly the curved wooden piece that gives this cat tree most of its height and which is one large, pretty heavy piece.