You can divide Bill Bryson's books into two categories. First are his more narrative works, which are generally travelogues (though I would count Thunderbolt Kid among this group as well), and comprise longer stories of his experiences supplemented with occasional diversions. Second would be his educational works, which choose a subject and explore its deepest chasms for nuggets of arcane interest.
The Body: A Guide for Occupants, as the name suggests, is of the second type, and its subject is self-evident. Bryson leads the reader through the body's many components, as well as branching of into related topics such as medicine. There are small anecdotes peppered throughout, but little in the way of narrative.
In his later years, Bryson has transitioned from a writer primarily of his first type to his second, and while his research is impressive and his writing always informative, I must say I like him best in a more narrative mood, as his gifts for description and flow often go unrealized in his educational books. There's also less room for his humor to reach its full momentum, though no Bryson book is without it’s funny lines. I enjoyed this one, but it may be a while before I read it again, and unlikely that it will enter tier one rotation along with his greatest works, like Thunderbolt Kid, A Walk in the Woods, and A Short History of Nearly Everything (his finest educational book).