Gamebooks are a genre of books that is also known as 'interactive fiction' and is almost always set in second person - following is an example of first, second, and third person.
(First) I ran down the path.
(Second) You run down the path.
(Third) Simba ran down the path.
Gamebooks, or interactive fiction, is named so for a very good reason. You will read a paragraph or two, then be presented with a list of choices of what you want to do. This means that you, the reader, have control over what the main character does and what happens in the plot. This genre is often compared to roleplaying, for it involves the reader's interaction for the story to progress.
What sort of choices?
Choices can vary from something simple as 'turn right' or 'open the door' to those a little more complex, such as 'lean out of the windowsill' or 'insert the key into the chest' to even the more ludicrous ones, such as 'set fire to the sack of potatoes' or 'scream'. As you can see, choices range from the mundane and simple to the bizzare and complex. They can involve the character avoiding catching a cold to even ending up killing the character.
Wait... you mean X could die?
Potentially, yes. Whenever you make a choice, it affects the character(s) future, which could include a premature death.
So how do I play?
To summarise the above, you will be presented with a paragraph (or two) to read and a list of choices following it, from which you must pick one to continue the adventure. If you feel comfortable on how to play, click the 'Close Window' button below, then start your first adventure!