I've been looking for a decent XML text which defines XML concisely and without wasting a lot of space on API examples and the usual "Let's say you want to organize your collection of movies - here's how you might write a DTD to do that". The choice is very limited. Which is surprising since XML is so popular, but not so surprising when people just 'use the API' most of the time. Also the specs for most of XML are readable if not as readable as possible. There's the relevant Nutshell book which is quite good and then there's one from the developmentor people. Needless to say - since developmentor people have played such a role in SOAP - that has a chapter on SOAP which I really think is out of place since SOAP is a solution to a completely different problem than XML and does not have any of the scope XML has.

There's an XML pocket reference from O'Reilly also - but what I've seen of it is to talkative for there to be enough space in 100 pages to cover XML nicely.

The perfect text would be super short sections on all the important topics - and it doesn't exist AFAIK. An opportunity perhaps.