Fairly easy to assemble w/hex wrench included! I modified the large top shelf to allow my cat to climb onto it a little easier! Simply drill two holes closer to the edge and move it over 3 inches! I have a muscular 25lb Norwegian Forest cat who loves the bigger room on the bottom and a 10lb female who loves the smaller room in the middle. My cats live on this thing day and night! It's also very easy to keep clean since the carpet nap is smooth and short! I purchased the black unit and it's absolutely beautiful, placed between my two red leather chairs!!! Your kitty will love you for buying this fine piece of furniture so, get it while it's on sale! You can't beat the price for the quality of workmanship! I'm going to buy one for the bedroom and one for the indoor patio! If you love your cat, buy one today and you won't be sorry! I paid a lot more for a lot less at a pet store! It's so safe and well made it won't tip over, even with two cats on the same side of the top two platforms!