Lots of pieces to put together, but each piece is numbered, and the pictures are easy to follow step by step. 
Comes with an attached wall anchor. I suggest using. Even against wall, with one cat, it tends to tip. Very nice quality. Very sturdy. My cat absolutely loves it.
My only complaint is the attached toys are silly. My cat tore one off immediately, but I do like that there is an attached hook for me to be able to make an attachment for my cats toys to hang off it.