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NANOVIEWS BIRDING BABYLON: A Soldier's Journal from Iraq. Jonathan Trouern-Trend. Sierra Club Books, $9.95.
While deployed in Iraq, Sgt. 1st Class Jonathan Trouern-Trend began a Web log to record and share his bird sightings. On walks around Camp Anaconda, a large base north of Baghdad, and on occasional forays into other parts of the country, Trouern-Trend spotted more than 100 species, a number of which were new additions to his "life list." At first he was surprised by the attention his blog received, but he thinks he knows now why people so appreciated his brief dispatches: "To read about something as universally familiar as the migration of birds, or watching ducks in a pond, fulfilled a need to know that something worthwhile or even magical was happening, even in the midst of suicide bombings and rocket attacks." Birding Babylon, a small but compelling book, is a compilation of some of the entries recorded over the course of his year-long tour of duty. The blog, which Trouern-Trend continues to update, can be read at http://birdingbabylon.blogspot.com-Amos Esty
NEGATIVE MATH: How Mathematical Rules Can Be Positively Bent. Alberto A. Martínez. Princeton University Press, $24.95.
Children seldom have much trouble with 2 + 2 = 4 or 2 × 2 = 4, but -2 × -2 = 4 is another matter. Why should two negatives make a positive? Whatever explanation you might suggest, why doesn't it also apply to -2 + -2 = -4? Generations of students have stumbled over this issue. One of them was Henri Beyle, who recalled of his school days in the 1790s: "When I spoke of my difficulty about minus times minus to one of the experts, he laughed in my face." Perhaps if Beyle's teachers had been more sympathetic and less dogmatic, he would have gone on to a career in mathematics instead of writing novels under the pen name Stendhal.
Beyle gets plenty of sympathy from Alberto A. Martínez, who shows that the concept of negative numbers has perplexed not just young students but also quite a few notable mathematicians, such as Sadi Carnot and Augustus de Morgan. And with good reason: The rule that minus times minus makes plus is not in fact grounded in some deep and immutable law of...