BSX book value is close to $8. You may ask abbot goodwill and intangibles. Goodwill and intangible are added when fair value of some assets are calculated. If the fair value comes down then goodwill and intangibles come down.
Next stop will be $60. Here's why: Guidant costs $28 billion, and BSX itself was worth $60 billion before Guidant purchase, so BSX today is really worth about $90 billion. The share price should be around $60 for a market cap of $90 billion.