Term Works! has already been touched on in earlier section of this Manual in the context of 'Document Disassembly'. But Term Works! offers an incredibly simple 'highlight & add' feature to make it easy to quickly move text into a book of your choice.
Term Works! is activated whenever you press <Alt-G> against highlighted text. (You can also activate Term Works! from the Pathagoras features menu.)
You choice of "Highlight & Add" versus a more deliberate Document Disassembly approach depends upon the specific project you have in mind. It you are adding a single piece of text, or just a few pieces, to a book, then Highlight & Add is definitely the way to go. Nothing could be quicker or easier. If, however, you need to add multiple building blocks of text from a single document, definitely consider the document disassembly procedures.