Morena Anna – awesome, let me make sure I understand what you are doing, that you will create a service where you will sell collections of books? Right to your end point, it makes a lot of sense to pre-guage demand for a number of reasons, as that will give you confidence and/or clarity that you have something that people want – it may also help you when you look to access books at wholesale prices – as you can show your site and also your demand you have equipped.
So – know your market, their needs and the best form is pre-orders – you start with a hypothesis around what you think maybe demanded/wanted and then you are doing to learn.
So – think about supply of books at wholesale, I do not know where you access this – I would think however that there must be a publishing association / group or retailers group – see if you can talk to a book retailer to see how and where they access their books and then approach them for their supply list – they will want to know what your plan is, etc so be ready with your data.
It maybe that you need to get going in a small way, and pay high wholesale prices before the wholesaler gives you more volume based pricing – even in a small way, if you are only on-line your costs may not be that high – you can get some momentum, learn and build up some sales which you can use to go back to get better pricing.
But first, test with users that your idea is something that people want. Andy