Source: Computer Networking First-Step by Wendell Odom (2004)

Example:

Often, learning something new can be a chore, particularly with computer technology. In fact, because you've obviously been searching for a book long enough to at least have opened up this one, you've probably looked at a few other books as well. There's no problem finding networking books. There are tons of them but almost all of them are geared toward people who want to be networking geeks, and the books frequently get deep and technical in a hurry. They're like the old joke where one guy walks through a door with an unseen long drop to the ground below, and his buddy shouts out, "Watch out for that first step. It's a doozy!"

Could you please explain that joke to me?