It sounds like you already have the book made in Word. But it's all in different documents.
If you're happy with the current layout in Word then you should try to either combine all the word files together. Or you should make PDFs of the each Word document. Using Acrobat Pro you can combine the PDFs into a single PDF.
The only reason to bring a Word file into InDesign is if you're going to change the layout of the document(s) to make them all consistent. If you're unsure how to use InDesign you should forego this route, or find someone who can help you with your project.
Again, if you're happy with the layout of the Word documents you should talk to your print provider about the best way to proceed in getting yourself to print.
InDesigns Book feature is managing InDesign files to manage the Chapters and synchronise styles and page numbers, chapter numbers etc. within InDesign file. It's sort of like a mini file manager for the Chapters of your InDesign files.