For example, not very many racebooks offer in-play horse racing – so if you are looking to bet on horse races in-play, narrow your search. Second-most important for us is the breadth of coverage. So, what do we look for in a racebook? Number one (as always) is the legitimacy and overall reputation of each operator. We list legal horse betting sites that have a verifiable history of processing wagers, paying out winners, and hosting fair bets.