A player to be booked bet is a bet that a named player will be shown a card during the match. If the referee shows him a yellow or a red, the bet wins. If he gets through the match without a card, it loses.
Rules differ between bookmakers on the details, so check your bookmaker's rules. The common questions are whether cards shown to a player on the bench count, whether cards after the final whistle count, whether a second yellow and the red that follows count as one card or two in card-points markets, and what happens if the player doesn't start.
Some bookmakers settle on 90 minutes only, and some include extra time. Non-starter rules vary too: some void the bet if the player doesn't start, others only if he doesn't play at all.
The inputs people look at are the player's fouls per 90, his position and role (defensive midfielders and full backs facing quick wingers pick up more cards), the referee, and the type of match. A tight derby is different from a one-sided game.
JOPP doesn't price card markets. Its markets are goals, assists, goal or assist, shots, shots on target, headers and outside the box.
Frequently asked questions
What does player to be booked mean?
It's a bet that a named player will receive a card, yellow or red, during the match. If he's shown a card, the bet wins.
Does a red card count for player to be booked?
Usually yes. A straight red is a card, so the bet wins. Check your bookmaker's rules for how second yellows are treated in card-points markets.
What happens if the player doesn't play?
Most bookmakers void the bet if the player takes no part, and some void it if he doesn't start. Check your bookmaker's rules.