What is a good introduction to Arthurian texts and theory available on Kindle?

I have been reading a lot of romances and different sources of Arthur's legends and tales.

I would like to find some kind of non fiction that discusses the context and history of the tales i have been reading.

But everything things I can find is almost completely inaccessible online. Goggle and Wikipedia has not been very helpful what is a good book on midevael romances that I can download on the kindle?

It's been impossible to find digital books and would like to read something that a good introduction to on King Arthur and romances. Especially non fiction history and literature analysis.

Thank you for your help!