Did you read the reviews on that site? They say it is not meant to hang on a wall. I can't tell how thick the sides are. It may be possible to attach a plywood back with screws and glue and a 1 x 3 at the top and bottom inside the plywood back to create attaching strips. Make sure these fit tight on the inside from side to side and pre-drill and drive in finish nails or trim screws through the sides and fill the holes. This would make it like the inside of a wall kitchen cabinet. Then you could drive screws through these strips into studs or attach to the wall with wing toggles. Try to attach it to at least 1 stud, preferably 2.
And fully loaded with books it could weigh 130 lbs, about 30 lbs on each of four fasteners.
If personal safety is involved like in the picture then each of four fasteners should be able to withstand a shearing force of a lot more than 130 lbs each. If you put a back on it you could use many fasteners to lessen the force on each.