Where is rest of the documentation?
All of the available DCMTK documentation is distributed in the DCMTK package. There is documentation about how to configure and run the programs. What is missing is documentation about how to use the libraries. Currently, the only way to learn how to use the libraries is to look at the example programs and do things the same way. Hopefully, some documentation will be written in the future and financial contributions would certainly reduce the waiting considerably.
Starting with release 3.5.3, a couple of simple examples of how to use the libraries are provided as part of the HTML documentation