Book: Migration Guide, revision 430ed5b9852c73719cf48bc9627e4f65b0282af0
Section: 7.5.2. Migrate Client-Cert SSL Authentication to Elytron

Legacy security realm (element) is not in legacy security subsystem (element). The beginning of the section should be reworded.

It is not obvious that the steps in the section requires steps from the previous section to be performed. The steps 2 and 3, and the resulting XML of undertow subsystem should be removed in such case. (Or, all required steps should be provided.)

There is invalid key-stores element in the resulting XML of elytron subsystem.

Links to security guides should be provided (referencing more information).