Bookmaker is a B+ book at best, a big fall from their heyday. Their betslip changes odds on you as you make a bet. It costs me 50-100k a year. Next, they harass winners and leave their payouts pending for days slowly asking for more and more KYC. This selfie, then that selfie, then fill out this spreadsheet. And after these delays, the BTC price has fluctuated and if it has fallen they short you. If BTC goes up, they pay you at the current market rate.
Bookmaker takes a big bet but they are shady too.