Hi @usrreddy972,
The wall will almost certainly be the better option, but we should determine what it is made of before deciding on a method.
Fixing to the wall is usually better as it doesn't add additional weight to the shelf, however, in your circumstance, you'll need a mid-support bracket which will have to be screwed to the bottom of the shelf so a combination of the two will be best.
You can use a Sandleford 19mm Chrome Pillar Centre for the mid-support with Sandleford 19mm Modern Rod Fitting Brackets on the walls. The provided screws should be fine, but if you find the screws for the mid-support bracket will poke through the top of the shelf due to their length, you can use these Zenith 8G x 16mm Countersunk Head Timber Screws to screw it in place.
Let me know what you think and if you have further questions, don't hesitate to ask.
Jacob
