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You say shelf pins - could that really work for 220 x 570 x 37mm blocks of worktop?
So basically I could just drill parallel holes in the sides and shove in a couple of shelf pins?
tbc-
Yes.
The weak point will be how the decor panels are attached to the carcasses, because this is where the combined weight of the shelves and books will be held. I usually use 6 4 X 25mm screws. Bear in mind it's not just the screws holding the weight though as the screws are pulling the panels into the side of the cabinet and create a fair amount of friction.
As far as the pins go chipboard handles compression forces very well, it's basically chips of wood glue together under a lot of pressure. This means there is no grain to split 5mm shelf pins have a stated maximum load of 12.5 kg per pin so if you put 6 pins per shelf in then the shelf+ load can be 75kgs. Would strongly recommend you make a jig for the holes from a bit of 2x1" or an offcut. This guarantees that all the pins will be at the same height.
Bobbo
Also @tbc
Most likely 15mm/18mm chipboard (depending on manufacturer) but will still hold it.
I'm with trunkie on this, if the shelf fits the space well then all of the weight will be transmitted down through the decor panel if you put a screw or shelf pin there it will not pull away. By using the tracks you are overcomplicating things significantly and making the space less usable as well.