Wiki Voyage, as part of the wikimedia project, has an incredibly useful tool simply called "Books". This features allows users the ability to collate various articles into a collection using the book creator tool. Wikivoyage books can be easily saved, rendered electronically in PDF, EPUB, ZIM or OpenDocument format, or ordered as a printed book.
The Help:Books page explains everything you need to know to use the feature.
Here is a sample workflow I use to create a custom guidebook for a particular region or regions.
The structure of Wiki Voyage is hierarchical with pages existing under categories. For example, "Category:Germany", is under "Category:Central_Europe" which is under "Category:Europe".