yes, you are correct, if using the repository module, when the user clicks to 'read' a PDF book, the PDF file will be opened. The browser will do what it deems appropriate based on the filetype, and what the end user has installed. For example, opening a PDF will open the file in the browser using Adobe reader if the user has Adobe reader installed, just like if it's an Excel spreadsheeet, opening an XLS file will launch Excel and open the file. If the browser cant figure out what to do, it usually asks the user to 'Open' or 'Save'.

If you are looking for an integrated solution where the contents of the book are displayed within the 'module' and allows paging, bookmarking, etc, then I don't believe any of the core modules or 'generic' modules will work for you. You need a specialized solution

I believe you only have 4 options.

1. check the DotNetNuke Marketplace to see if a module exists that will meet your needs

2. check SnowCovered to see if a module exists that will meet your needs

3. advertise for a DotNetNuke Developer/Consultant to write you a module

4. write the module yourself