It is always easier to break a long document which often runs into several hundred pages into smaller chunks that are individual InDesign documents (file extension .indd) that can be easily managed. How many chunks you break is entirely up to your liking.
You can combine all these individual InDesign documents into an InDesign book (file extension. indb). To create a book, open the File menu, go to the New submenu and select Book… This will open the Save dialog box and ask you to save the book file. Give it a name and click OK. This will create the book and open the Book panel.
In the following example, we have taken two .indd files. However, you can choose any number of files by clicking the + symbol at the bottom of the panel. Once all the .indd files are added, you will see that the page numbers are made continuous.
The icon next to the first document in the Book panel indicates the style source. It means, this document is a source for whatever paragraph or character style changes that you make. You can select any document as a style source.
The best part about using the Book panel is that this style source can be synchronized with all other documents in the panel by clicking the double arrow icon in the bottom of the panel. This will tell InDesign to look for style elements in the first document and implement them in the subsequent documents.
You will get a confirmation once the synchronization is complete.