Getting a site to done usually means a lot of fussing and fretting to get everything just right. You've built out content types and views and blocks and menus (and if you haven't, get back to Chapter 1) and done a bunch of other configuration (see Chapter 7) and the site is indisputably 90% built. It's just that the final 10% can easily take as much time as you've already put in. If the site is high visibility and has to look great and work easily, keep going until, as the song goes, you've done did everything that needs done.
This chapter touches on advanced configuration but mostly uses glue code to polish off DefinitiveDrupal.org with modded cupholders and custom rims. Glue code is theming functions or modules written to meet site-specific needs. (See Part V, Module Development and in particular Chapter 18). You'll even see a spin-off module made for contributing to Drupal.org in the process.