Time to grow
The theme in all of this is "growth". Since its release, Unity has made a huge splash in the game development world by offering a suite of tools that blew the lid off of 3D browser-based gaming, while making it easier for people without serious C-based programming knowledge to develop for once-unfathomable devices.
It's a complete cliché, but practice really is the one thin line separating you from developing those big projects you put up in jars on the shelf at the beginning of the book. Start building a game with what you know. With each project, set a new attainable challenge for yourself. This book has taught you how to set lights in a flat-looking hallway environment. But you've heard this term "lightmap" when reading about 3D games and models. What's that all about? Well, why not build a new game using the skills you've already developed, and commit to incorporating one lightmapped object in it? When you finish the game, you'll have added one extra tool to your tool belt...