i am trying to setup a website where a large amount of Ebooks is going to be offered both individually along with a subscription is going to be offered to some library - so anybody from that library can click on the website with no paywall (so, according to IP). think JSTOR, for instance, or perhaps a newspaper archive.

I am really confident with WordPress (may even dev plug ins on their behalf) although not sure something similar to this is available inside the Wordpress wordpress plugin (or group of wordpress plugin) mobile phone industry's. If that's the case, i would like to know!

Otherwise, can someone indicate a platform that's a) hopefully FOSS, b) could be developed with php/sql of some kind, and c) is user-friendly enough that the client can enter new Ebooks herself and set them up available?

A relatively popular product is Greenstone. It's broadly used and FOSS. Unsure concerning the implementation language, however i don't believe it's PHP (or SQL, for your matter). Regardless, In my opinion you could do this IP-limitation with a couple type of webserver-level configuration.

Additionally, it certainly supports different amounts of user access, so that some customers can use the administration interface to be able to add documents. It's pretty easy for the reason that regard.