Pretty easy to assemble.  We have 2 cats that absolutely love it!  They chase each other up and down all day long and love to take turns sleeping "bowl-o-kitty" as we call it.  One of the best purchases we've made for the cats. With all the jumping and rough housing they do on it, it does tend to wobble a bit but has never tipped over but our cats aren't particularly large, it would be absolutely perfect if it had a weighted base to make it a little more stable.