Here are my faves:
--The Owen and Mzee books, because the photos are gorgeous, the story amazing and the text straightforward and not condescending;
--All of Sy Montgomery's books, but particularly "The Man-Eating Tigers of Sundurban," which, like the others, features an outrageously cool animal story and a "you-are-the-detective" tone that kids love; and finally,
--"What the World Eats" was a huge hit with kids and adults at our house over the holidays. It's a beautiful book that shows what families all over the world consume in a week and includes lots of other fascinating and well-presented data about world populations. Thanks to Alison's store for recommending it!

A Drop of Water by Walter Wick;
Frogs by Nic Bishop;
and, especially
Poop: A Natural History of the Unmentionable by Nicola Davies (Poop is currently listed as "Permanently out of stock" in the original edition from Candlewick Press. Oh, woe! How can the ultimate science book on a topic of such universal and pressing interest tread the dire path of out-of-printness????)

Does Phineas Gage fit in here? If so, I heart PHINEAS GAGE: A GRUESOME TRUE STORY of something I've forgotten the rest of the subtitle. It is AWESOME, however.

TOO-TALL TINA by Donna Pitino (Kane Press, 2005) helps build self-esteem and math measurement skills at the same time. The math concepts are woven into a fictional story about Tina, who has experienced a growth spurt over the summer and is not sure how she feels about it, especially when she begins third grade and finds she's the tallest one.

What to Eat by Marion Nestle. It's not a diet guide, but more of a manual on how to make informed choices. It shows how politics in the food industry determine what ends up in our grocery stores and ultimately on our plates and what all those buzz words like all natural, organic, and whole grain really mean.

One of my favorite children's non-fiction authors is the team of Robin Page and Steve Jenkins. They've done some amazing stuff, including my 2 favorites: _What Do You Do With a Tail Like This?_, a Caldecott Honor book in 2004, and _Sisters and Brothers: Sibling Relationships in the Animal World_. Both are incredibly illustrated, fascinating, and very readable.

Oh, yes, PHINEAS GAGE! Here are my other picks for the WHAT category:
AN AMERICAN PLAGUE, by Jim Murphy;
THE RACE TO SAVE THE LORD GOD BIRD, by Philip Hoose;
A SEED IS SLEEPY and AN EGG IS QUIET, both by Diana Hutts Aston and Sylvia Long
FOSSIL FISH FOUND ALIVE, by Sally M. Walker
WRITING MAGIC, by Gail Carson Levine

I want to start off with one of my all time favorites even though it has an awful layout--Round Buildings, Square Buildings, and Buildings that Wiggle like a Fish by Philip Issacson. And that the Magic School Bus series made science so much fun. Middle Passage by Tom Feelings, Come Back Salmon by Molly Cone, Freight Train by Donald Crews, It's Perfectly Normal by Robie Harris, The Red-Eyed Tree Frog by Joy Crowly. And again I have to mention my fellow nonfiction bloggers at I.N.K. Interesting Nonfiction for Kids who have created some truly wonderful books.

I want to add a title that I really enjoyed, Pippa's First Summer by Catherine Badgley, a wonderful non-anthropomorphic tale of a young bat's first year, complete with a terrific explanation of how bats navigate, and other particulars of their day-to-day lives, published by Mitten Press in Ann Arbor.

The Tall Man by Chloe Hooper (Australian) which is Australian current history, politics, philosophy, why, wherefore, and how far.

Russell Freedman is not only the king of 'who" books but has done so many great "what" books that one cannot begin to list them.