Shelving advice

[Ifnottodaywhen]

I want to put up some heavy duty shelves for books. All the ones I've seen so far look to be fairly flimsy and I'm fed-up of buying stuff online that turns out not to fit for purpose.

Has anybody got any advice where to look for sturdy shelves?

TIA

My son has a billion books and has a room kitted out in garage shelving which is robust and has a large capacity to hold books.

It’s an industrial look like high might not suit your room aesthetic.