This is an oft-asked question. I may sound like a shill for Olympic, but there really isn't any other book that is very close. Sure, OLY offers some worthless props (who will win coin toss, etc) at -115 juice, but they clearly have the greatest number, greatest variety of props including many "player props". Payouts never a problem with Olympic.
Some people say 5 Dimes has great props. Typically they are posted later than Oly and not as many. Plus 5 Dimes is irritating in that you have to look through all their betting options before you find the props.
Carib used to have a decent array of NFL player props but then bagged them in mid-season. Bet365 has some ok ones at times.
Pinnacle and Cascade have a small number from time to time and WSEX has some, too, but none of them comes close to Olympic.
While there are plenty of people who bash Oly's props as being too much juice, etc., the bashers are never able to suggest any books that consistently have better props.