This book is not bad. But I couldn't really very confidently say it was all that good either. Compared to Bryson's travel writings and his history of nearly everything I think other reviewers are justified in saying that it is on the duller side. I certainly had to force my way through, and I wouldn't consider myself uninterested by the subject matter.
That said, it was worth pushing through to the end because - as another reviewer has noted - the last chapter is easily the best. If you want a demolition job on the many and varied conspiracy theories which posit someone else as the auther of Shakespeare's works, this chapter will give you one which is amusing and devastating in equal measure.
Another nice element is that it does give a fairly good look into the world of late Elizibethan and early Jacobean theatre, which is quite interesting, though somewhat disappointingly for someone with the mythbusting potential previously alluded to, he does trot out a serious of victorian myths regarding the Puritans - who did close down the theatres, but not because they were against fun.
All in all, it's not as funny as Bryson usually manages, and doesn't really distiguish itself as a work of history (even popular history). Still, as I said, its not bad, and is a reasonable introduction to the Bard