We don't "recommend" online sports books for a couple of reasons:
A) It's not legal yet
and
B) It's not legal yet
All I can personally do is tell you where I play(ed) at recently.
CRIS (Bookmaker), 5Dimes, Heritage and YouWager would be on the list
of books I've done business with and it worked out fine. Online
play is not for everyone. There is absolutely a risk involved.
At this time it's play-at-your-own-risk. I don't sweat it much but
my tolerance for risk may be much different than yours.
Currently researching BitCoin books and it looks promising as far
as accessibility for US players. Updates here and on the front page throughout
the months ahead.