Sad to say there isn't much.
The problem is that photographers tend to write books about the technical side. Anything else seems to be written by linguists, psychologists, sociologists and historians. They all miss the point and leave a big empty space in the middle - which is why I bang on about this subject here. If you hadn't realised it, I am bouncing my views and ideas off you so that I can refine and focus my thoughts with the intention of writing the book that is so obviously needed. I have mentioned here and there that one day I will do my Doctorate - I wasn't joking. The book (or, more properly, the thesis) will not be definitive or cover anywhere near what needs to be covered - but I hope it will provide a framework within which a meaningful dialogue can take place. And then hopefully people will be able to start writing books that are actually of some use.
That being said, there are one or two books that are definitely worth reading. There is a lot to disagree with in some of them (you should see my margin notes) but you they will introduce you to some important concepts and get you thinking.
On Photography - Susan Sontag
This is an essential read. It is well written and is a good first book. I disagree with most of what she writes - but that isn't the point. Sontag looks at Photography from a different perspective and starts you thinking.
Dialogue With Photography - Hill & Cooper
Interviews with 22 major photographers, including Strand, Lartigue, Brassai, Adams, Newhall... Another essential read. It lives on my bedside table.
Camera Lucida - Roland Barthes
It is his final book. Whilst there is a lot I disagree with (again) it is splendid as a series of meditations on Photography. It is worthwhile reading his other essays as well.
Occam's Razor - Bill Jay
An antidote to everything photographic. 'An outside-in view of contemporary photography' - and it is. He keeps it all in perspective with essays such as 'Madonna Made Me Do It' and 'Creating A Viable Dialogue Situation'. Great fun with a very serious point.
There are one or two others but these are the 'must reads'. I always recommend them to students.