I ended up rearranging our living room to fit an 80 x 60 cage in! What I did was buy a second hand book case - that went up the wall - used it as shelving. Moved a cupboard and coffee table upstairs to a bedroom to make floorspace and contents of cupboard went on the shelf unit. I used the coffee table upstairs as a kind of book shelf/occasional table. This gave me space on the floor in a bay window )ie an area that didn’t get walked past much so it wouldn’t be kicked or tripped over).
By the time I’d finished I had space for a 100cm cage - and wished I’d got that instead of the 80cm one.
From what you say you’re thinking of converting a book shelf into a hamster cage? Is that right?
How about replacing the boom shelf with an IKEA kallax unit (linked below). An 80 x 50 cage fits well on top of one of those and you have storage underneath.
What species of hamster do you have?
KALLAX white, Shelving unit, 77x77 cm - IKEA