Shelving Strength Q’s

Currently looking at embarking on a first ‘ground up’ DIY project (not too complicated for my first one) which involves construction of some bespoke cabinets and shelving in a little alcove we’ve got.
Focusing on the shelving, my plan currently is to have three levels of single piece 1 1/2” hardwood cut to fit around two of the alcove edges (note the corner isn’t quite square). These aren’t going to be floating but be screwed into from several tapered support ‘brackets’ (also 1 1/2” wide and around 2 1/2” at wall edge) which secure into wall studs with two pocket holes on the top side that’ll be covered by the shelves anyway. Due to only using wall studs the supports will have to be around 2 feet apart as well...
Do you guys think this set up will be sturdy enough for say up to 20kg per shelf, or anything else you think I could include to make better? Main thing I’m concerned about is only having the supports secured at the top and whether the lever effect may then cause cracking in the plaster etc below them? Maybe I can’t get around having to screw them in at the bottom as well..

Why not ditch the brackets and just use 1/2" thick battens at the sides and back of the alcove, which should be more than enough to support books etc.

Blup

I agree with ‘blip’ the use of battens is a much more elegant solution, I’ve put loads of shelving up, this will be more than adequate for this weight.