No introductory book is going to cover everything. Are you looking for an easier book? A more detailed one? A book with more data? A book with more alternative theories?
If you want to know "everything" about x-bar (or anything else in syntax) then you may want to start reading about the history of syntax. In fact, Carnie covers that pretty well. But to fully understand it, knowing how the theory developed is a good idea.
The trouble is that the "same" theory evolves over time and also gets more complex as it addresses more complex data.