Asking the question probably answers it to a certain extent. Its either do it or don’t. Making shelves for people in return for money is in theory easy. The issues are demand and supply. Firstly there needs to be the connection between people tripping across piles of books and getting shelves to solve this problem. Secondly there is the idea of the shelf. Primarily it should be furniture. My reasoning for this is it is the best return on investment. Anything stuck to the wall can not be rearranged and if removed leaves holes. Holes in any wall are not viewed as a positive feature and doubly so if the property is rented or you are thinking of moving on in the future. Shelves as furniture are an asset. They look well and if made well, they last well. They can be rearranged, moved, sold or given to someone who will appreciate good quality. On the supply side there are numerous sets of shelves and bookcases out there. The issues there are value for money too. You shouldn’t need a mortgage, nor should you be forced to buy low cost kits that after the slightest damage turn out to be temporary.
Reading Pratchett I find I agree with the character Vimes when he looks at the price and quality of boots. The rich pay 150 for a pair of boots that are waterproof and last for 4 – 5 years. The poor buy boots that cost 40 and leak almost straight away and buy a pair each year. So the poor pay more and still have wet feet. Good quality shelves or bookcases are in the same category. They look well and keep the books well. They last well and tag along with you through life. They are worth something if you want to sell them. I like value for money – either getting it or giving it, but I am living in a society where a company pays more for advertising than manufacture. Needs more thought.