very difficult and time consuming to assemble on your own, but not impossible. no instructions at all. the only major issue was when screwing in the lid at the very end, it's almost not big enough where the screws will fit into it on both sides to screw in and secure. i worked on that for like 20 minutes going back and forth loosening one end and trying to pull the other so it would fit with the screw in it. it did work in the end but i got lucky. either the lid needs to be slightly bigger or longer screws are needed.
once it's put together tho it is very nice looking and plenty of room for my hamster, i'm also not worried about him chewing through it which is why i went with this instead of a wooden one.