I wrote a "tips" post about how to play a room with red herrings in it. Click here for that post.
In an escape room, a red herring is a tool, puzzle, lock, or any other element that looks important but is actually useless. They are distractions. "Red herring" is a term that comes from a method that fox hunters used to use to train their dogs to track foxes. They would release a fox, and before they released the dog to track the fox, the hunters would drag some red herring (fish) across the fox's trail. The goal was to train the dog not to be distracted by the scent of the red herring and stay focused on the scent of the fox.
In other words, the goal of the red herring was to keep them focused on the clearly communicated task: catch the fox. The trainers communicated the goal to the dogs, but game designers who put red herrings in rooms without at least giving a clue about which puzzle players should focus on have less respect for their players than dog trainers have for their dogs. If players are not clued in on what the task is, they will follow the smell of the red herring without knowing they are supposed to track a fox.
There's a lot of debate in the escape room world about red herrings. Some designers often use them intentionally to distract players from their true objective. My opinion about red herrings is this: Red herrings reveal a lack of creativity or budget. And I'm not alone in that view. I recently surveyed over 900 escape room enthusiasts, and less than 4% of them think it's a good idea to intentionally put red herrings in a room on a regular basis, and I wonder if those people were game designers who have run out of puzzle ideas. If you're going to use a red herring to steal the time of players, you might as well leave out the red herring and take time off the clock. Respect your players, and fill their time with fun, not junk.
Game designers who intentionally use red herrings in a room to cause confusion are missing the point of escape rooms, and they don't have enough respect for the time and intelligences of their players. They choose to focus on the challenge instead of on entertaining their guests. If less than 4% of players like red herrings, red herrings must not add to the enjoyment of a room. I don't know many people who enjoy feeling frustrated, and solving a pointless puzzle is very frustrating.
Rhett Hildebrandt, owner of The Quandary Escape Rooms in Chicago, Illinois, writes, "In general, the difficulty of the puzzle should be equivalent to the value of the thing unlocked. So a very difficult puzzle should unlock something of great value that will greatly progress the game. Red herrings unlock things of 0 value, therefore the red herring puzzles should be 0 in difficulty...which is nothing...which means they shouldn't exist."
In the best rooms, everything in the room has a purpose, and I do mean everything. That doesn't mean designers can't decorate a room, but they should be careful in their decoration selection. It's fine to have a picture of trees in a room, but it's something entirely different to have a pointless book in the room that lists different species of trees. An article of clothing in a room usually isn't a red herring, but an article of clothing with a tag that has a pointless number written on it with a Sharpie is a red herring. A ticking clock on the wall set to the correct time is not a red herring, but a clock that is pointlessly stuck on a time is a red herring. A rocking horse is not a red herring, but a rocking horse with letters drawn on it with markers is a red herring. A replica of the Statue of Liberty on a shelf isn't a red herring, but a pointless chart with information about the Statue of Liberty is a red herring. If players regularly mistake a decoration for a clue, the decoration should be removed from the room and replaced with something less distracting and more immersive.
One of the things I love most about escape rooms is that they are challenges that reveal skill, teamwork, intelligence, and other useful qualities, but red herrings add an element of luck into a room. If a team luckily works on the important puzzles and doesn't get to the red herrings, they could luckily be more successful than a more skilled team. That's not to say that it's impossible to get good at spotting red herrings. That is definitely a skill that can be developed. Over the years, we've gotten pretty good at recognizing them, and when we know we're going into a room with red herrings, we start by finding locks then looking for keys/codes to those locks rather than starting with puzzle solves. In other words, we enter the rooms as skeptics rather than as characters immersed in a story. That's just not a fun way to play a room, even when the designer tries to make the red herring part of the room's story.
Books are tricky. They seem to fit well into many different rooms as decoration, but prop books almost always distract people from real puzzles. For this reason, I suggest that designers glue closed the books that are purely there for decoration.
I do not mean to imply that I've never enjoyed a room that had red herrings in it. I have, many times, but no room with multiple red herrings has ever made my list of favorite rooms. I like immersive games that keep the adrenaline pumping, and nothing removes me from an immersive scenario like a red herring, especially an intentional red herring.