Thanks to the Internet you no longer need a dictionary or encyclopedia in your home. Web sites like Wikipedia are often better, and versions of traditional dictionaries and encyclopedias are usable online.
But you still need a good atlas. There's no substitute for large pages with high resolution printing. And while programs like Google Earth do things no print atlas can do, a paper atlas comes with a wealth of interpretive content.
Interpretation is what makes the DK Great World Atlas so terrific. It's got maps, sure. But it's also got satellite photos, and images at night, and bits of text highlighting how a place fits together both geologically and sociologically. The editorial content is excellent and the printing is beautiful. It's expensive at $63, but well worth it.
If you're atlas-happy a good supplement is the DK World History Atlas. This book is like those flip charts you had in grade school showing migrations across Europe, only global, detailed, and not condescending. It's more a book you read than a collection of maps, and interesting for that.