don't take this the wrong way, but the best bonuses is not the top priority of top cappers. Think of it this way: You can get a 1000%
bonus, but when it comes time to request a w/d, you will probably waste alot of your time given the runaround. So my advice to you is to look for a quality book, which many have spoken, which ones they are and take it from there. Think of the bonuses as secondary. Payout, customer service, betting options, and among others are more benecial to you in the long run.
Vegas is actually the best place to bet as you know you never have to sweat the payout. And the catch with this is they don't give out bonuses. Same with offshores, the best places try to minimize the bonuses as their department knows that other factors keeps their clients loyal, and not bonuses where you have hit & run bettors trying to gain off a small deposit.
Just my 2cents but hopefully you get the picture I am trying to tell you.
Good Luck in whatever book you choose and Happy New Year.